Entity Framework Core 2 for the Enterprise

HHerzl

4.93/5 (139 votes)

Dec 12, 2016

CPOL

21 min read

241905

Entity Framework Core 2 for the Enterprise

GitHub repository

Introduction

Design and implement architecture for enterprise applications it's a big challenge, there is a common question in this point: What is the the best way following the best practices according to selected technology in our company.

This guide uses .NET Core, so We'll work with Entity Framework Core, but these concepts apply for another technologies like Dapper or another ORM.

In fact, We'll take a look at the common requirements to design enterprise architect in this article.

The sample database provided in this guide represents an online store.

This is the stack for this solution:

Entity Framework Core
ASP.NET Core
xUnit for unit tests
xUnit for integration tests
Identity Server 4

Payment Gateway

Online Store needs to receive payments through payment service, for this case I created a payment gateway named Rothschild House, you can found source code in this link.

Rothschild House allows to receive payments with credit cards.

This payment gateway is for demonstration purposes only.

Running Payment Gateway

Run RothschildHouse solution, solution has these projects:

Project	Runs on port
`RothschildHouse`	18000
`RothschildHouse.IdentityServer`	19000

The above output is the configuration for Identity Server, RothschildHouse.IdentityServer provides authentication and authorization to receive payments.

Credentials for Online Store

User name	Password
administrator@onlinestore.com	onlinestore1

These credentials are provided by Rothschild House to clients.

Payment Schema

RothschildHouse project contains PaymentDbContext class, this class provides the model to process payments.

Entities:

Person
CreditCard
PaymentMethod
PaymentTransaction

Payment Data

PaymentDbContext accepts these customers:

User name	Password	Card holder name	Issuing network	Card number	Expiration Date	CVV
jameslogan@walla.com	wolverine	James Logan	Visa	4024007164051145	6/1/2024	987
ororo_munroe@yahoo.com	storm	Ororo Munroe	MasterCard	5473913699329307	1/1/2023	147

Background

According to my experience, enterprise applications should have the following levels:

Database: Is the relational database management system
Common: Contains common objects for layers (e.g. Loggers, Mappers, Extensions)
Core: Contains objects related to business logic and database access
Testing: Contains tests for back-end (units and integration)
External Services (optional): Contains invocations for external services (ASMX, WCF, RESTful)
Security: Is an API that provides authentication and authorization
Presentation: Is the user interface

Architecture: Big Picture

DATABASE	SQL Server	DATABASE
COMMON	Extensions, Helpers (Loggers and Mappers)	BACK-END
CORE	Services, Exceptions, DbContext, Entities, Configurations and Data Contracts	BACK-END
TESTING	Unit tests and Integration tests	BACK-END
EXTERNAL SERVICES	ASMX, WCF, RESTful	BACK-END
SECURITY	Authentication and Authorization (Identity Server \| Others)	BACK-END
PRESENTATION	UI Frameworks (Angular \| ReactJS \| Vue.js \| Others)	FRONT-END

Prerequisites

Skills

Before to continuing, keep in mind we need to have the folllowing skills in order to understand this guide:

Object Oriented Programming
Aspect Oriented Programming
Object Relational Mapping
Design Patterns

Software

.NET Core
Visual Studio 2017
SQL Server instance (local or remote)
SQL Server Management Studio

Using the Code
Code improvements
Points of Interest
Related Links

Using the Code

Chapter 01 - Database

Take a look for sample database to understand each component in architecture. In this database there are 4 schemas:

Dbo
HumanResources
Sales
Warehouse

Each schema represents a division for online store company, keep this in mind because all code is designed following this aspect; at this moment this code only implements features for Warehouse and Sales schemas.

All tables have a primary key with one column and have columns for creation, last update and concurrency token.

Tables

Schema	Name
`dbo`	`ChangeLog`
`dbo`	`ChangeLogExclusion`
`dbo`	`Country`
`dbo`	`CountryCurrency`
`dbo`	`Currency`
`dbo`	`EventLog`
`HumanResources`	`Employee`
`HumanResources`	`EmployeeAddress`
`HumanResources`	`EmployeeEmail`
`Sales`	`Customer`
`Sales`	`OrderDetail`
`Sales`	`OrderHeader`
`Sales`	`OrderStatus`
`Sales`	`PaymentMethod`
`Sales`	`Shipper`
`Warehouse`	`Location`
`Warehouse`	`Product`
`Warehouse`	`ProductCategory`
`Warehouse`	`ProductInventory`

You can found the scripts for database in this link: Online Store Database Scripts on GitHub.

Please remember: This is a sample database, only for demonstration of concepts.

Chapter 02 - Core Project

Core project represents the core for solution, in this guide Core project includes docmain and business logic.

Online Store works with .NET Core, the naming convention is .NET naming convention, so it's very useful to define a naming convention table to show how to set names in code, something like this:

Identifier	Case	Example
Namespace	PascalCase	`Store`
Class	PascalCase	`Product`
Interface	I prefix + PascalCase	`ISalesRepository`
Method	Verb in PascalCase + Noun in PascalCase	`GetProducts`
Async Method	Verb in PascalCase + Noun in PascalCase + Async sufix	`GetOrdersAsync`
Property	PascalCase	`Description`
Parameter	camelCase	`connectionString`

This convention is important because it defines the naming guidelines for architecture.

This is the structure for OnlineStore.Core project:

Domain
Domain\Configurations
Domain\DataContracts
Business
Business\Contracts
Business\Responses

Inside of Domain We'll place all entities, in this context, entity means a class that represents a table or view from database, sometimes entity is named POCO (Plain Old Common language runtime Object) than means a class with only properties not methods nor other things (events); according to wkempf feedback it's necessary to be clear about POCOs, POCOs can have methods and events and other members but it's not common to add those members in POCOs.

For Domain\Configurations, There are object definitions related to mapping classes for database.

Inside of Domain and Domain\Configurations, there is one directory per schema.

Inside of Business, There are interfaces and implementations for services, in this case, the services will contain the methods according to use cases (or something like that) and those methods must perform validations and handle exceptions related to business.

For Business\Responses, These are the responses definitions: single, list and paged to represent the results from services.

We'll inspect the code to understand these concepts but the review would be with one object per level because the remaining code is similar.

Domain

Please take a look at POCOs, We're using nullable types instead of native types because nullable are easy to evaluate if property has value or not, that's more similar to database model.

In Domain there are two interfaces: IEntity and IAuditEntity, IEntity represents all entities in our application and IAuditEntity represents all entities that allows to save audit information: create and last update; as special point if we have mapping for views, those classes do not implement IAuditEntity because a view doesn't allow insert, update and delete operations.

OrderHeader class:

using System;
using System.Collections.ObjectModel;
using OnlineStore.Core.Domain.Dbo;
using OnlineStore.Core.Domain.HumanResources;

namespace OnlineStore.Core.Domain.Sales
{
    public class OrderHeader : IAuditableEntity
    {
        public OrderHeader()
        {
        }

        public OrderHeader(long? id)
        {
            ID = id;
        }

        public long? ID { get; set; }

        public short? OrderStatusID { get; set; }

        public DateTime? OrderDate { get; set; }

        public int? CustomerID { get; set; }

        public int? EmployeeID { get; set; }

        public int? ShipperID { get; set; }

        public decimal? Total { get; set; }

        public string CurrencyID { get; set; }

        public Guid? PaymentMethodID { get; set; }

        public int? DetailsCount { get; set; }

        public long? ReferenceOrderID { get; set; }

        public string Comments { get; set; }

        public string CreationUser { get; set; }

        public DateTime? CreationDateTime { get; set; }

        public string LastUpdateUser { get; set; }

        public DateTime? LastUpdateDateTime { get; set; }

        public byte[] Timestamp { get; set; }

        public virtual OrderStatus OrderStatusFk { get; set; }

        public virtual Customer CustomerFk { get; set; }

        public virtual Employee EmployeeFk { get; set; }

        public virtual Shipper ShipperFk { get; set; }

        public virtual Currency CurrencyFk { get; set; }

        public virtual PaymentMethod PaymentMethodFk { get; set; }

        public virtual Collection<OrderDetail> OrderDetails { get; set; }
    }
}

Keys

Also there is an important aspect for Entity Layer, all entities that allow create operation have the key property as nullable type, this is related to philosophy in software develoment.

Lets take a look on this, We'll use the Product entity as sample:

public class Product
{
	public int? ID { get; set; }
	
	public string Name { get; set; }
}

Lets create an instance of Product class:

var entity = new Product(); // ID property has null value instead of 0

Now lets create a new Product in database:

using (var ctx = new OnlineStore())
{
	// Create an instance of Product class
	// The ID property will be initialized with null
	// This is logic because the entity is not saved in database yet
	var newProduct = new Product
	{
		Name = "Product sample"
	};
	
	// Add instance of product in memory
	ctx.Products.Add(newProduct);
	
	// Save all changes in database
	await ctx.SaveChangesAsync();
	
	// Now the ID property has the generated value from database side
	//
	// To validate if property has value We can peform a check like this:
	//
	// if (newProduct.ID.HasValue)
	// {
	//  // Get value from property and use it...
	// }
}

So, now change the type for ID property from int? to int, the property value will be initialized with 0 value, 0 it's an integer, please consider if in some cases there are ID that can be negatives , so isn't enough to validate if property value is greather than zero.

This explanation makes sense?, let me know in comments :)

Data Layer

This solution doesn't work with Repository pattern anymore, later I'll add an explanation why.

We're working with Entity Framework Core in this guide, so We need to have a DbContext and objects that allow mapping database objects like tables and views.

Naming Issue

Repository versus DbHelper versus Data Access Object.

This issue is related to naming objects, some years ago I used DataAccessObject as suffix to class that contain database operatios (select, insert, update, delete, etc). Other developers used DbHelper as suffix to represent this kind of objects, at my beggining in EF I learned about repository design pattern, so from my point of view I prefer to use Repository suffix to name the object that contains database operations.

OnlineStoreDbContext class:

using Microsoft.EntityFrameworkCore;
using OnlineStore.Core.Domain.Configurations;
using OnlineStore.Core.Domain.Configurations.Dbo;
using OnlineStore.Core.Domain.Configurations.HumanResources;
using OnlineStore.Core.Domain.Configurations.Sales;
using OnlineStore.Core.Domain.Configurations.Warehouse;
using OnlineStore.Core.Domain.Dbo;
using OnlineStore.Core.Domain.HumanResources;
using OnlineStore.Core.Domain.Sales;
using OnlineStore.Core.Domain.Warehouse;

namespace OnlineStore.Core.Domain
{
    public class OnlineStoreDbContext : DbContext
    {
        public OnlineStoreDbContext(DbContextOptions<OnlineStoreDbContext> options)
            : base(options)
        {
        }

        public DbSet<ChangeLog> ChangeLogs { get; set; }

        public DbSet<ChangeLogExclusion> ChangeLogExclusions { get; set; }

        public DbSet<CountryCurrency> CountryCurrencies { get; set; }

        public DbSet<Country> Countries { get; set; }

        public DbSet<Currency> Currencies { get; set; }

        public DbSet<EventLog> EventLogs { get; set; }

        public DbSet<Employee> Employees { get; set; }

        public DbSet<EmployeeAddress> EmployeeAddresses { get; set; }

        public DbSet<EmployeeEmail> EmployeeEmails { get; set; }

        public DbSet<ProductCategory> ProductCategories { get; set; }

        public DbSet<ProductInventory> ProductInventories { get; set; }

        public DbSet<Product> Products { get; set; }

        public DbSet<ProductUnitPriceHistory> ProductUnitPriceHistories { get; set; }

        public DbSet<Location> Locations { get; set; }

        public DbSet<Customer> Customers { get; set; }

        public DbSet<OrderDetail> OrderDetails { get; set; }

        public DbSet<OrderHeader> OrderHeaders { get; set; }

        public DbSet<OrderStatus> OrderStatuses { get; set; }

        public DbSet<OrderSummary> OrderSummaries { get; set; }

        public DbSet<PaymentMethod> PaymentMethods { get; set; }

        public DbSet<Shipper> Shippers { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            // Apply all configurations

            modelBuilder
                .ApplyConfiguration(new ChangeLogConfiguration())
                .ApplyConfiguration(new ChangeLogExclusionConfiguration())
                .ApplyConfiguration(new CountryCurrencyConfiguration())
                .ApplyConfiguration(new CountryConfiguration())
                .ApplyConfiguration(new CurrencyConfiguration())
                .ApplyConfiguration(new EventLogConfiguration())
                ;

            modelBuilder
                .ApplyConfiguration(new EmployeeConfiguration())
                .ApplyConfiguration(new EmployeeAddressConfiguration())
                .ApplyConfiguration(new EmployeeEmailConfiguration())
                ;

            modelBuilder
                .ApplyConfiguration(new ProductCategoryConfiguration())
                .ApplyConfiguration(new ProductConfiguration())
                .ApplyConfiguration(new ProductUnitPriceHistoryConfiguration())
                .ApplyConfiguration(new ProductInventoryConfiguration())
                .ApplyConfiguration(new LocationConfiguration())
                ;

            modelBuilder
                .ApplyConfiguration(new CustomerConfiguration())
                .ApplyConfiguration(new OrderDetailConfiguration())
                .ApplyConfiguration(new OrderHeaderConfiguration())
                .ApplyConfiguration(new OrderStatusConfiguration())
                .ApplyConfiguration(new OrderSummaryConfiguration())
                .ApplyConfiguration(new PaymentMethodConfiguration())
                .ApplyConfiguration(new ShipperConfiguration())
                ;

            base.OnModelCreating(modelBuilder);
        }
    }
}

OrderHeaderConfiguration class:

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using OnlineStore.Core.Domain.Sales;

namespace OnlineStore.Core.Domain.Configurations.Sales
{
    public class OrderHeaderConfiguration : IEntityTypeConfiguration<OrderHeader>
    {
        public void Configure(EntityTypeBuilder<OrderHeader> builder)
        {
            // Mapping for table
            builder.ToTable("OrderHeader", "Sales");

            // Set key for entity
            builder.HasKey(p => p.ID);

            // Set identity for entity (auto increment)
            builder.Property(p => p.ID).UseSqlServerIdentityColumn();

            // Set mapping for columns
            builder.Property(p => p.OrderStatusID).HasColumnType("smallint").IsRequired();
            builder.Property(p => p.OrderDate).HasColumnType("datetime").IsRequired();
            builder.Property(p => p.CustomerID).HasColumnType("int").IsRequired();
            builder.Property(p => p.EmployeeID).HasColumnType("int");
            builder.Property(p => p.ShipperID).HasColumnType("int");
            builder.Property(p => p.Total).HasColumnType("decimal(12, 4)").IsRequired();
            builder.Property(p => p.CurrencyID).HasColumnType("varchar(10)");
            builder.Property(p => p.PaymentMethodID).HasColumnType("uniqueidentifier");
            builder.Property(p => p.DetailsCount).HasColumnType("int").IsRequired();
            builder.Property(p => p.ReferenceOrderID).HasColumnType("bigint");
            builder.Property(p => p.Comments).HasColumnType("varchar(max)");
            builder.Property(p => p.CreationUser).HasColumnType("varchar(25)").IsRequired();
            builder.Property(p => p.CreationDateTime).HasColumnType("datetime").IsRequired();
            builder.Property(p => p.LastUpdateUser).HasColumnType("varchar(25)");
            builder.Property(p => p.LastUpdateDateTime).HasColumnType("datetime");

            // Set concurrency token for entity
            builder.Property(p => p.Timestamp).ValueGeneratedOnAddOrUpdate().IsConcurrencyToken();

            // Add configuration for foreign keys
            builder
                .HasOne(p => p.OrderStatusFk)
                .WithMany(b => b.Orders)
                .HasForeignKey(p => p.OrderStatusID);

            builder
                .HasOne(p => p.CustomerFk)
                .WithMany(b => b.Orders)
                .HasForeignKey(p => p.CustomerID);

            builder
                .HasOne(p => p.ShipperFk)
                .WithMany(b => b.Orders)
                .HasForeignKey(p => p.ShipperID);
        }
    }
}

How about Unit of Work? in EF 6.x was usually create a repository class and unit of work class: repository provided operations for database access and unit of work provided operations to save changes in database; but in EF Core it's a common practice to have only repositories and no unit of work; anyway for this code we have added two methods in Repository class: CommitChanges and CommitChangesAsync, so just to make sure that inside of all data writing mehotds in repositories call CommitChanges or CommitChangesAsync and with that design we have two definitions working on our architecture.

How about async operations? In previous versions of this post I said We'll implement async operations in the last level: REST API, but I was wrong about that because .NET Core it's more about async programming, so the best decision is handle all database operations in async way using the Async methods that Entity Framework Core provides.

For the last version of this article, We have a payment gateway named Rothschild House, this API provides payment authorization, this API below to external services layer.

Later, I'll add a section to explain about payment gateway.

Stored Procedures versus LINQ Queries

In data layer, there is a very interesting point: How we can use stored procedures? For the current version of EF Core, there isn't support for stored procedures, so we can't use them in a native way, inside of DbSet, there is a method to execute a query but that works for stored procedures not return a result set (columns), we can add some extension methods and add packages to use classic ADO.NET, so in that case we need to handle the dynamic creation of objects to represent the stored procedure result; that makes sense? if we consume a procedure with name GetOrdersByMonth and that procedure returns a select with 7 columns, to handle all results in the same way, we'll need to define objects to represent those results, that objects must define inside of DataLayer\DataContracts namespace according to our naming convention.

Inside of enterprise environment, a common discussion is about LINQ queries or stored procedures. According to my experience, I think the best way to solve that question is: review design conventions with architect and database administrator; nowadays, it's more common to use LINQ queries in async mode instead of stored procedures but sometimes some companies have restrict conventions and do not allow to use LINQ queries, so it's required to use stored procedure and we need to make our architecture flexible because we don't say to developer manager "the business logic will be rewrite because Entity Framework Core doesn't allow to invoke stored procedures"

As We can see until now, assuming We have the extension methods for EF Core to invoke stored procedures and data contracts to represent results from stored procedures invocations, Where do we place those methods? It's preferable to use the same convention so we'll add those methods inside of contracts and repositories; just to be clear if we have procedures named Sales.GetCustomerOrdersHistory and HumanResources.DisableEmployee; we must to place methods inside of Sales and HumanResources repositories.

You can also read more about this point in this link.

Just to be clear: STAY AWAY FROM STORED PROCEDURES!

The previous concept applies in the same way for views in database. In addition, we only need to check that repositories do not allow add, update and delete operations for views.

Change Tracking

Inside of OnLineStoreDbContextExtensions class there is a method with name GetChanges, that method get all changes from DbContext through ChangeTracker and returns all changes, so those values are saved in ChangeLog table in CommitChanges method. You can update one existing entity with business object, later you can check your ChangeLog table:

ChangeLogID ClassName    PropertyName   Key  OriginalValue          CurrentValue           UserName   ChangeDate
----------- ------------ -------------- ---- ---------------------- ---------------------- ---------- -----------------------
1           Employee     FirstName      1    John                   John III               admin      2017-02-19 21:49:51.347
2           Employee     MiddleName     1                           Smith III              admin      2017-02-19 21:49:51.347
3           Employee     LastName       1    Doe                    Doe III                admin      2017-02-19 21:49:51.347

(3 row(s) affected)

As We can see all changes made in entities will be saved on this table, as a future improvement we'll need to add exclusions for this change log. In this guide we're working with SQL Server, as I know there is a way to enable change tracking from database side but in this post I'm showing to you how you can implement this feature from back-end; if this feature is on back-end or database side will be a decision from your leader. In the timeline we can check on this table all changes in entities, some entities have audit properties but those properties only reflect the user and date for creation and last update but do not provide full details about how data change.

Business

Naming Issue

Controller versus Service versus Business Object

There is a common issue in this point, How we must to name the object that represents business operations: for first versions of this article I named this object as BusinessObject, that can be confusing for some developers, some developers do not name this as business object because the controller in Web API represents business logic, but Service is another name used by developers, so from my point of view is more clear to use Service as sufix for this object. If we have a Web API that implements business logic in controller we can ommit to have services, but if there is business layer it is more useful to have services, these classes must to implement logic business and controllers must invoke service's methods.

Business Layer: Handle Related Aspects To Business

Logging: We need to have a logger object, that means an object that logs on text file, database, email, etc. all events in our architecture; we can create our own logger implementation or choose an existing log. We have added logging with package Microsoft.Extensions.Logging, in this way we're using the default log system in .NET Core, we can use another log mechanism but at this moment we'll use this logger, inside of every method in controllers and business objects, there is a code line like this: Logger?.LogInformation("{0} has been invoked", nameof(GetOrdersAsync));, in this way we make sure invoke logger if is a valid instance and ths using of nameof operator to retrieve the name of member without use magic strings, after we'll add code to save all logs into database.
Business exceptions: The best way to handle messaging to user is with custom exceptions, inside of business layer, We'll add definitions for exceptions to represent all handle errors in architecture.
Transactions: as We can see inside of Sales business object, we have implemented transaction to handle multiple changes in our database; inside of CreateOrderAsync method, we invoke methods from repositories, inside of repositories we don't have any transactions because the service is the responsible for transactional process, also we added logic to handle exceptions related to business with custom messages because we need to provide a friendly message to the end-user.
There is a CloneOrderAsync method, this method provides a copy from existing order, this is a common requirement on ERP because it's more easy create a new order but adding some modifications instead of create the whole order there are cases where the sales agent create a new order but removing 1 or 2 lines from details or adding 1 or 2 details, anyway never let to front-end developer to add this logic in UI, the API must to provide this feature.
GetPostOrderModelAsync method in SalesService provides the required information to create an order, information from foreign keys: products and anothers. With this method We are providing a model that contains the list for foreign keys and in that way We reduce the work from front-end to know how to create create order operation.

Service class:

using Microsoft.Extensions.Logging;
using OnlineStore.Core.Business.Contracts;
using OnlineStore.Core.Domain;

namespace OnlineStore.Core.Business
{
    public abstract class Service : IService
    {
        protected bool Disposed;
        protected readonly ILogger Logger;

        public Service(ILogger logger, OnlineStoreDbContext dbContext, IUserInfo userInfo)
        {
            Logger = logger;
            DbContext = dbContext;
            UserInfo = userInfo;
        }

        public void Dispose()
        {
            if (Disposed)
                return;

            DbContext?.Dispose();

            Disposed = true;
        }

        public OnlineStoreDbContext DbContext { get; }

        public IUserInfo UserInfo { get; set; }
    }
}

SalesService class:

using System;
using System.Collections.ObjectModel;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using OnlineStore.Core.Business.Contracts;
using OnlineStore.Core.Business.Requests;
using OnlineStore.Core.Business.Responses;
using OnlineStore.Core.Domain;
using OnlineStore.Core.Domain.Dbo;
using OnlineStore.Core.Domain.Repositories;
using OnlineStore.Core.Domain.Sales;
using OnlineStore.Core.Domain.Warehouse;

namespace OnlineStore.Core.Business
{
    public class SalesService : Service, ISalesService
    {
        public SalesService(ILogger<SalesService> logger, OnlineStoreDbContext dbContext, IUserInfo userInfo)
            : base(logger, dbContext, userInfo)
        {
        }

        public async Task<IPagedResponse<Customer>> GetCustomersAsync(int pageSize = 10, int pageNumber = 1)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(GetCustomersAsync));

            var response = new PagedResponse<Customer>();

            try
            {
                // Get query
                var query = DbContext.Customers;

                // Set information for paging
                response.PageSize = pageSize;
                response.PageNumber = pageNumber;
                response.ItemsCount = await query.CountAsync();

                // Retrieve items, set model for response
                response.Model = await query
                    .Paging(pageSize, pageNumber)
                    .ToListAsync();
            }
            catch (Exception ex)
            {
                response.SetError(Logger, nameof(GetCustomersAsync), ex);
            }

            return response;
        }

        public async Task<IPagedResponse<Shipper>> GetShippersAsync(int pageSize = 10, int pageNumber = 1)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(GetShippersAsync));

            var response = new PagedResponse<Shipper>();

            try
            {
                // Get query
                var query = DbContext.Shippers;

                // Set information for paging
                response.PageSize = pageSize;
                response.PageNumber = pageNumber;
                response.ItemsCount = await query.CountAsync();

                // Retrieve items, set model for response
                response.Model = await query
                    .Paging(pageSize, pageNumber)
                    .ToListAsync();
            }
            catch (Exception ex)
            {
                response.SetError(Logger, nameof(GetShippersAsync), ex);
            }

            return response;
        }

        public async Task<IPagedResponse<Currency>> GetCurrenciesAsync(int pageSize = 10, int pageNumber = 1)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(GetCurrenciesAsync));

            var response = new PagedResponse<Currency>();

            try
            {
                // Get query
                var query = DbContext.Currencies;

                // Set information for paging
                response.PageSize = pageSize;
                response.PageNumber = pageNumber;
                response.ItemsCount = await query.CountAsync();

                // Retrieve items, set model for response
                response.Model = await query
                    .Paging(pageSize, pageNumber)
                    .ToListAsync();
            }
            catch (Exception ex)
            {
                response.SetError(Logger, nameof(GetCurrenciesAsync), ex);
            }

            return response;
        }

        public async Task<IPagedResponse<PaymentMethod>> GetPaymentMethodsAsync(int pageSize = 10, int pageNumber = 1)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(GetPaymentMethodsAsync));

            var response = new PagedResponse<PaymentMethod>();

            try
            {
                // Get query
                var query = DbContext.PaymentMethods;

                // Set information for paging
                response.PageSize = pageSize;
                response.PageNumber = pageNumber;
                response.ItemsCount = await query.CountAsync();

                // Retrieve items, set model for response
                response.Model = await query
                    .Paging(pageSize, pageNumber)
                    .ToListAsync();
            }
            catch (Exception ex)
            {
                response.SetError(Logger, nameof(GetPaymentMethodsAsync), ex);
            }

            return response;
        }

        public async Task<IPagedResponse<OrderInfo>> GetOrdersAsync(int? pageSize, int? pageNumber, short? orderStatusID, int? customerID, int? employeeID, int? shipperID, string currencyID, Guid? paymentMethodID)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(GetOrdersAsync));

            var response = new PagedResponse<OrderInfo>();

            try
            {
                // Get query
                var query = DbContext
                    .GetOrders(orderStatusID, customerID, employeeID, shipperID, currencyID, paymentMethodID);

                // Set information for paging
                response.PageSize = (int)pageSize;
                response.PageNumber = (int)pageNumber;
                response.ItemsCount = await query.CountAsync();

                // Retrieve items, set model for response
                response.Model = await query
                    .Paging((int)pageSize, (int)pageNumber)
                    .ToListAsync();

                response.Message = string.Format("Page {0} of {1}, Total of rows: {2}", response.PageNumber, response.PageCount, response.ItemsCount);

                Logger?.LogInformation(response.Message);
            }
            catch (Exception ex)
            {
                response.SetError(Logger, nameof(GetOrdersAsync), ex);
            }

            return response;
        }

        public async Task<ISingleResponse<OrderHeader>> GetOrderAsync(long id)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(GetOrderAsync));

            var response = new SingleResponse<OrderHeader>();

            try
            {
                // Retrieve order by id
                response.Model = await DbContext.GetOrderAsync(new OrderHeader(id));
            }
            catch (Exception ex)
            {
                response.SetError(Logger, nameof(GetOrderAsync), ex);
            }

            return response;
        }

        public async Task<ISingleResponse<CreateOrderRequest>> GetCreateOrderRequestAsync()
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(GetCreateOrderRequestAsync));

            var response = new SingleResponse<CreateOrderRequest>();

            try
            {
                // Retrieve products list
                response.Model.Products = await DbContext.GetProducts().ToListAsync();

                // Retrieve customers list
                response.Model.Customers = await DbContext.Customers.ToListAsync();
            }
            catch (Exception ex)
            {
                response.SetError(Logger, nameof(GetCreateOrderRequestAsync), ex);
            }

            return response;
        }

        public async Task<ISingleResponse<OrderHeader>> CreateOrderAsync(OrderHeader header, OrderDetail[] details)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(CreateOrderAsync));

            var response = new SingleResponse<OrderHeader>();

            // Begin transaction
            using (var transaction = await DbContext.Database.BeginTransactionAsync())
            {
                try
                {
                    // todo: Retrieve available warehouse to dispatch products
                    var warehouses = await DbContext.Locations.ToListAsync();

                    foreach (var detail in details)
                    {
                        // Retrieve product by id
                        var product = await DbContext.GetProductAsync(new Product(detail.ProductID));

                        // Throw exception if product no exists
                        if (product == null)
                            throw new NonExistingProductException(string.Format(SalesDisplays.NonExistingProductExceptionMessage, detail.ProductID));

                        // Throw exception if product is discontinued
                        if (product.Discontinued == true)
                            throw new AddOrderWithDiscontinuedProductException(string.Format(SalesDisplays.AddOrderWithDiscontinuedProductExceptionMessage, product.ID));

                        // Throw exception if quantity for product is invalid
                        if (detail.Quantity <= 0)
                            throw new InvalidQuantityException(string.Format(SalesDisplays.InvalidQuantityExceptionMessage, product.ID));

                        // Set values for detail
                        detail.ProductName = product.ProductName;
                        detail.UnitPrice = product.UnitPrice;
                        detail.Total = product.UnitPrice * detail.Quantity;
                    }

                    // Set default values for order header
                    if (!header.OrderDate.HasValue)
                        header.OrderDate = DateTime.Now;

                    header.OrderStatusID = 100;

                    // Calculate total for order header from order's details
                    header.Total = details.Sum(item => item.Total);
                    header.DetailsCount = details.Count();

                    // Save order header
                    DbContext.Add(header, UserInfo);

                    await DbContext.SaveChangesAsync();

                    foreach (var detail in details)
                    {
                        // Set order id for order detail
                        detail.OrderHeaderID = header.ID;
                        detail.CreationUser = header.CreationUser;

                        // Add order detail
                        DbContext.Add(detail, UserInfo);

                        await DbContext.SaveChangesAsync();

                        // Create product inventory instance
                        var productInventory = new ProductInventory
                        {
                            ProductID = detail.ProductID,
                            LocationID = warehouses.First().ID,
                            OrderDetailID = detail.ID,
                            Quantity = detail.Quantity * -1,
                            CreationUser = header.CreationUser,
                            CreationDateTime = DateTime.Now
                        };

                        // Save product inventory
                        DbContext.Add(productInventory);
                    }

                    await DbContext.SaveChangesAsync();

                    response.Model = header;

                    // Commit transaction
                    transaction.Commit();

                    Logger.LogInformation(SalesDisplays.CreateOrderMessage);
                }
                catch (Exception ex)
                {
                    response.SetError(Logger, nameof(CreateOrderAsync), ex);
                }
            }

            return response;
        }

        public async Task<ISingleResponse<OrderHeader>> CloneOrderAsync(long id)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(CloneOrderAsync));

            var response = new SingleResponse<OrderHeader>();

            try
            {
                // Retrieve order by id
                var entity = await DbContext.GetOrderAsync(new OrderHeader(id));

                if (entity == null)
                    return response;

                // Create a new instance for order and set values from existing order
                response.Model = new OrderHeader
                {
                    ID = entity.ID,
                    OrderDate = entity.OrderDate,
                    CustomerID = entity.CustomerID,
                    EmployeeID = entity.EmployeeID,
                    ShipperID = entity.ShipperID,
                    Total = entity.Total,
                    Comments = entity.Comments
                };

                if (entity.OrderDetails?.Count > 0)
                {
                    response.Model.OrderDetails = new Collection<OrderDetail>();

                    foreach (var detail in entity.OrderDetails)
                    {
                        // Add order detail clone to collection
                        response.Model.OrderDetails.Add(new OrderDetail
                        {
                            ProductID = detail.ProductID,
                            ProductName = detail.ProductName,
                            UnitPrice = detail.UnitPrice,
                            Quantity = detail.Quantity,
                            Total = detail.Total
                        });
                    }
                }
            }
            catch (Exception ex)
            {
                response.SetError(Logger, nameof(CloneOrderAsync), ex);
            }

            return response;
        }

        public async Task<IResponse> CancelOrderAsync(long id)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(CancelOrderAsync));

            var response = new Response();

            try
            {
                // Retrieve order by id
                var entity = await DbContext.GetOrderAsync(new OrderHeader(id));

                if (entity == null)
                    return response;

                // Restrict remove operation for orders with details
                if (entity.OrderDetails.Count > 0)
                    throw new ForeignKeyDependencyException(string.Format(SalesDisplays.RemoveOrderExceptionMessage, id));

                // Delete order
                DbContext.Remove(entity);

                await DbContext.SaveChangesAsync();

                Logger?.LogInformation(SalesDisplays.DeleteOrderMessage);
            }
            catch (Exception ex)
            {
                response.SetError(Logger, nameof(CancelOrderAsync), ex);
            }

            return response;
        }
    }
}

In Business it's better to have custom exceptions for represent errors instead of send simple string messages to client, obviously the custom exception must have a message but in logger there will be a reference about custom exception. For this architecture these are the custom exceptions:

Business Exceptions
Name	Description
`AddOrderWithDiscontinuedProductException`	Represents an exception adding order with a discontinued product
`ForeignKeyDependencyException`	Represents an exception deleting an order with detail rows
`DuplicatedProductNameException`	Represents an exception adding product with existing name
`NonExistingProductException`	Represents an exception adding order with non existing product

Chapter 03 - Putting All Code Together

We need to create a OnlineStoreDbContext instance, that instance works with SQL Server, in OnModelCreating method, all configurations are applied to ModelBuilder instance.

Later, there is an instance of SalesService created with a valid instance of OnlineStoreDbContext to get access for service's operations.

Get All

This is an example to retrieve orders:

// Create logger instance
var logger = LoggingHelper.GetLogger<ISalesService>();

// Create application user
var userInfo = new UserInfo();

// Create options for DbContext
var options = new DbContextOptionsBuilder<OnlineStoreDbContext>()
    .UseSqlServer("YourConnectionStringHere")
    .Options;

// Create instance of business object
// Set logger, application user and context for database
using (var service = new SalesService(logger, userInfo, new OnlineStoreDbContext(options)))
{
    // Declare parameters and set values for paging
	var pageSize = 10;
	var pageNumber = 1;

    // Get response from business object
	var response = await service.GetOrderHeadersAsync(pageSize, pageNumber);

	// Validate if there was an error
	var valid = !response.DidError;
}

GetOrderHeadersAsync method in SalesService retrieves rows from Sales.OrderHeader table as a generic list.

Get by Key

This is an example to retrieve an entity by key:

// Create logger instance
var logger = LoggingHelper.GetLogger<ISalesService>();

// Create application user
var userInfo = new UserInfo();

// Create options for DbContext
var options = new DbContextOptionsBuilder<OnlineStoreDbContext>()
    .UseSqlServer("YourConnectionStringHere")
    .Options;

// Create instance of business object
// Set logger, application user and context for database
using (var service = new SalesService(logger, userInfo, new OnlineStoreDbContext(options)))
{
    // Declare parameters and set values for paging
	var id = 1;

    // Get response from business object
	var response = await service.GetOrderHeaderAsync(id);

	// Validate if there was an error
	var valid = !response.DidError;
	
	// Get entity
	var entity = response.Model;
}

For incoming versions of this article, there will be samples for another operations.

Chapter 04 - Mocker

Mocker it's a project that allows to create rows in Sales.OrderHeader, Sales.OrderDetail and Warehouse.ProductInventory tables for a range of dates, by default Mocker creates rows for one year.

Program class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using OnlineStore.Common.Helpers;
using OnlineStore.Core.Domain.Sales;

namespace OnlineStore.Mocker
{
    public class Program
    {
        static readonly ILogger Logger;

        static Program()
        {
            Logger = LoggingHelper.GetLogger<Program>();
        }

        public static void Main(string[] args)
            => MainAsync(args).GetAwaiter().GetResult();

        static async Task MainAsync(string[] args)
        {
            var year = DateTime.Now.AddYears(-1).Year;
            var ordersLimitPerDay = 3;

            foreach (var arg in args)
            {
                if (arg.StartsWith("/year:"))
                    year = Convert.ToInt32(arg.Replace("/year:", string.Empty));
                else if (arg.StartsWith("/ordersLimitPerDay:"))
                    ordersLimitPerDay = Convert.ToInt32(arg.Replace("/ordersLimitPerDay:", string.Empty));
            }

            var start = new DateTime(year, 1, 1);
            var end = new DateTime(year, 12, DateTime.DaysInMonth(year, 12));

            if (start.DayOfWeek == DayOfWeek.Sunday)
                start = start.AddDays(1);

            do
            {
                if (start.DayOfWeek != DayOfWeek.Sunday)
                {
                    await CreateDataAsync(start, ordersLimitPerDay);

                    Thread.Sleep(1000);
                }

                start = start.AddDays(1);
            }
            while (start <= end);
        }

        static async Task CreateDataAsync(DateTime date, int ordersLimitPerDay)
        {
            var random = new Random();

            var warehouseService = ServiceMocker.GetWarehouseService();
            var salesService = ServiceMocker.GetSalesService();

            var customers = (await salesService.GetCustomersAsync()).Model.ToList();
            var currencies = (await salesService.GetCurrenciesAsync()).Model.ToList();
            var paymentMethods = (await salesService.GetPaymentMethodsAsync()).Model.ToList();
            var products = (await warehouseService.GetProductsAsync(10, 1)).Model.ToList();

            Logger.LogInformation("Creating orders for {0}", date);

            for (var i = 0; i < ordersLimitPerDay; i++)
            {
                var header = new OrderHeader
                {
                    OrderDate = date,
                    CreationDateTime = date
                };

                var selectedCustomer = random.Next(0, customers.Count - 1);
                var selectedCurrency = random.Next(0, currencies.Count - 1);
                var selectedPaymentMethod = random.Next(0, paymentMethods.Count - 1);

                header.CustomerID = customers[selectedCustomer].ID;
                header.CurrencyID = currencies[selectedCurrency].ID;
                header.PaymentMethodID = paymentMethods[selectedPaymentMethod].ID;

                var details = new List<OrderDetail>();

                var detailsCount = random.Next(1, 5);

                for (var j = 0; j < detailsCount; j++)
                {
                    var detail = new OrderDetail
                    {
                        ProductID = products[random.Next(0, products.Count - 1)].ID,
                        Quantity = (short)random.Next(1, 5)
                    };

                    if (details.Count > 0 && details.Count(item => item.ProductID == detail.ProductID) == 1)
                        continue;

                    details.Add(detail);
                }

                await salesService.CreateOrderAsync(header, details.ToArray());

                Logger.LogInformation("Date: {0}", date);
            }

            warehouseService.Dispose();
            salesService.Dispose();
        }
    }
}

Now in the same window terminal, we need to run the following command: dotnet run and if everything works fine, We can check the data in database for OrderHeader, OrderDetail and ProductInventory tables.

How Mocker works? set a range for dates and a limit of orders per day, then iterates all days in date range except sundays because We're assuming create order process is not allowed on sundays; then create the instance of DbContext and Services, arranges data using a random index to get elements from products, customers, currencies and payment methods; then invokes the CreateOrderAsync method.

You can adjust the range for dates and orders per day to mock data according to your requirements, once the Mocker has finished you can check the data on your database.

Chapter 05 - Payment Gateway

The payment gateway implements Identity Server as authentication and authorization API.

Payment Gateway has two projects:

RothschildHouse.IdentityServer
RothschildHouse

RothschildHouse.IdentityServer

Payment gateway implements in-memory configuration for Identity Server.

Identity Server API for Payment Gateway runs on port 18000.

In browser, open http://localhost:18000/.well-known/openid-configuration url:

{  
   "issuer":"http://localhost:18000",
   "jwks_uri":"http://localhost:18000/.well-known/openid-configuration/jwks",
   "authorization_endpoint":"http://localhost:18000/connect/authorize",
   "token_endpoint":"http://localhost:18000/connect/token",
   "userinfo_endpoint":"http://localhost:18000/connect/userinfo",
   "end_session_endpoint":"http://localhost:18000/connect/endsession",
   "check_session_iframe":"http://localhost:18000/connect/checksession",
   "revocation_endpoint":"http://localhost:18000/connect/revocation",
   "introspection_endpoint":"http://localhost:18000/connect/introspect",
   "device_authorization_endpoint":"http://localhost:18000/connect/deviceauthorization",
   "frontchannel_logout_supported":true,
   "frontchannel_logout_session_supported":true,
   "backchannel_logout_supported":true,
   "backchannel_logout_session_supported":true,
   "scopes_supported":[  
      "RothschildHouseApi",
      "offline_access"
   ],
   "claims_supported":[  

   ],
   "grant_types_supported":[  
      "authorization_code",
      "client_credentials",
      "refresh_token",
      "implicit",
      "password",
      "urn:ietf:params:oauth:grant-type:device_code"
   ],
   "response_types_supported":[  
      "code",
      "token",
      "id_token",
      "id_token token",
      "code id_token",
      "code token",
      "code id_token token"
   ],
   "response_modes_supported":[  
      "form_post",
      "query",
      "fragment"
   ],
   "token_endpoint_auth_methods_supported":[  
      "client_secret_basic",
      "client_secret_post"
   ],
   "subject_types_supported":[  
      "public"
   ],
   "id_token_signing_alg_values_supported":[  
      "RS256"
   ],
   "code_challenge_methods_supported":[  
      "plain",
      "S256"
   ]
}

In order to allow connections, We need to add configuration for API resources and clients, this configuration is in Config class:

using System.Collections.Generic;
using System.Security.Claims;
using IdentityModel;
using IdentityServer4.Models;

namespace RothschildHouse.IdentityServer
{
    public static class Config
    {
        public static IEnumerable<ApiResource> GetApiResources()
            => new List<ApiResource>
            {
                new ApiResource("RothschildHouseAPI", "Rothschild House API")
            };

        public static IEnumerable<Client> GetClients()
            => new List<Client>
            {
                new Client
                {
                    ClientId = "onlinestoreclient",
                    AllowedGrantTypes = GrantTypes.ResourceOwnerPassword,
                    ClientSecrets =
                    {
                        new Secret("onlinestoreclientsecret1".Sha256())
                    },
                    AllowedScopes =
                    {
                        "RothschildHouseAPI"
                    },
                    Claims =
                    {
                        new Claim(JwtClaimTypes.Role, "Customer")
                    }
                }
            };
    }
}

Let's take a look in Startup code:

using IdentityServer4.Services;
using IdentityServer4.Validation;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using RothschildHouse.IdentityServer.Domain;
using RothschildHouse.IdentityServer.Services;
using RothschildHouse.IdentityServer.Validation;

namespace RothschildHouse.IdentityServer
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            /* Setting up dependency injection */

            // For DbContext
            services.AddDbContext<AuthDbContext>(options => options.UseInMemoryDatabase("Auth"));

            // Password validator and profile
            services
                .AddTransient<IResourceOwnerPasswordValidator, ResourceOwnerPasswordValidator>()
                .AddTransient<IProfileService, ProfileService>();

            /* Identity Server */

            // Use in-memory configurations

            services
                .AddIdentityServer()
                .AddDeveloperSigningCredential()
                .AddInMemoryApiResources(Config.GetApiResources())
                .AddInMemoryClients(Config.GetClients());

            // Add authentication
            services
                .AddAuthentication()
                .AddIdentityServerAuthentication();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
                app.UseDeveloperExceptionPage();

            /* Seed AuthDbContext in-memory */

            var authDbContext = app
                .ApplicationServices
                .CreateScope()
                .ServiceProvider
                .GetService<AuthDbContext>();

            authDbContext.SeedInMemory();

            app.UseIdentityServer();
        }
    }
}

RothschildHouse

RothschildHouse implements in-memory configuration for Identity Server.

RothschildHouse runs on port 19000.

Configuration for Startup class:

using System;
using System.IO;
using System.Reflection;
using IdentityServer4.AccessTokenValidation;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Diagnostics;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using RothschildHouse.Controllers;
using RothschildHouse.Domain;
using Swashbuckle.AspNetCore.Swagger;

namespace RothschildHouse
{
#pragma warning disable CS1591
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            /* Setting up dependency injection */

            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

            services.AddTransient<ILogger<TransactionController>, Logger<TransactionController>>();

            // In-memory DbContext
            services.AddDbContext<PaymentDbContext>(options =>
            {
                options
                    .UseInMemoryDatabase("Payment")
                    .ConfigureWarnings(w => w.Ignore(InMemoryEventId.TransactionIgnoredWarning));
            });

            // Identity Server
            services
                .AddAuthentication("Bearer")
                .AddIdentityServerAuthentication(options =>
                {
                    var settings = new IdentityServerAuthenticationOptions();

                    Configuration.Bind("IdentityServerSettings", settings);

                    options.Authority = settings.Authority;
                    options.RequireHttpsMetadata = settings.RequireHttpsMetadata;
                    options.ApiName = settings.ApiName;
                    options.ApiSecret = settings.ApiSecret;
                });

            // Register the Swagger generator, defining 1 or more Swagger documents
            services.AddSwaggerGen(options =>
            {
                options.SwaggerDoc("v1", new Info { Title = "RothschildHouse API", Version = "v1" });

                // Get xml comments path
                var xmlFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.xml";
                var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);

                // Set xml path
                options.IncludeXmlComments(xmlPath);
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
                app.UseDeveloperExceptionPage();

            // Seed initial data in-memory for DbContext
            var paymentDbContext = app
                .ApplicationServices
                .CreateScope()
                .ServiceProvider
                .GetService<PaymentDbContext>();

            paymentDbContext.SeedInMemory();

            app.UseAuthentication();

            // Enable middleware to serve generated Swagger as a JSON endpoint.
            app.UseSwagger();

            // Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.), specifying the Swagger JSON endpoint.
            app.UseSwaggerUI(options =>
            {
                options.SwaggerEndpoint("/swagger/v1/swagger.json", "RothschildHouse API V1");
            });

            app.UseMvc();
        }
    }
#pragma warning restore CS1591
}

Code for TransactionController class:

using System;
using System.Linq;
using System.Net;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using RothschildHouse.Domain;
using RothschildHouse.Requests;
using RothschildHouse.Responses;

namespace RothschildHouse.Controllers
{
#pragma warning disable CS1591
    [Route("api/v1/[controller]")]
    [ApiController]
    [Authorize]
    public class TransactionController : ControllerBase
    {
        readonly ILogger<TransactionController> Logger;
        readonly PaymentDbContext DbContext;

        public TransactionController(ILogger<TransactionController> logger, PaymentDbContext dbContext)
        {
            Logger = logger;
            DbContext = dbContext;
        }
#pragma warning restore CS1591

        /// <summary>
        /// Places a new payment
        /// </summary>
        /// <param name="request">Payment request</param>
        /// <returns>A payment response</returns>
        [HttpPost("Payment")]
        public async Task<IActionResult> PostPaymentAsync([FromBody]PostPaymentRequest request)
        {
            Logger?.LogDebug("'{0}' has been invoked", nameof(PostPaymentAsync));

            var creditCards = await DbContext.GetCreditCardByCardHolderName(request.CardHolderName).ToListAsync();

            var creditCard = default(CreditCard);

            var last4Digits = request.CardNumber.Substring(request.CardNumber.Length - 4);

            if (creditCards.Count > 1)
                creditCard = creditCards.FirstOrDefault(item => item.CardNumber == request.CardNumber);
            else if (creditCards.Count == 1)
                creditCard = creditCards.First();

            if (creditCard == null)
                return BadRequest(string.Format("There is not record for credit card with last 4 digits: {0}.", last4Digits));

            /* Check credit card information */

            if (!creditCard.IsValid(request))
                return BadRequest(string.Format("Invalid information for card payment."));

            /* Check if customer has available credit (limit) */

            if (!creditCard.HasFounds(request))
                return BadRequest(string.Format("There are no founds to approve the payment."));

            using (var txn = await DbContext.Database.BeginTransactionAsync())
            {
                try
                {
                    var paymentTxn = new PaymentTransaction
                    {
                        PaymentTransactionID = Guid.NewGuid(),
                        CreditCardID = creditCard.CreditCardID,
                        ConfirmationID = Guid.NewGuid(),
                        Amount = request.Amount,
                        PaymentDateTime = DateTime.Now
                    };

                    DbContext.PaymentTransactions.Add(paymentTxn);

                    creditCard.AvailableFounds -= request.Amount;

                    await DbContext.SaveChangesAsync();

                    txn.Commit();

                    Logger?.LogInformation("The payment for card with last 4 digits: '{0}' was successfully. Confirmation #: {1}", last4Digits, paymentTxn.ConfirmationID);

                    var response = new PaymentResponse
                    {
                        ConfirmationID = paymentTxn.ConfirmationID,
                        PaymentDateTime = paymentTxn.PaymentDateTime,
                        Last4Digits = creditCard.Last4Digits
                    };

                    return Ok(response);
                }
                catch (Exception ex)
                {
                    Logger?.LogCritical("There was an error on '{0}': {1}", nameof(PostPaymentAsync), ex);

                    txn.Rollback();

                    return new ObjectResult(ex.Message)
                    {
                        StatusCode = (int)HttpStatusCode.InternalServerError
                    };
                }
            }
        }
    }
}

Payment request:

using System;
using System.ComponentModel.DataAnnotations;

namespace RothschildHouse.Requests
{
    /// <summary>
    /// Represents the model for payment request
    /// </summary>
    public class PostPaymentRequest
    {
        /// <summary>
        /// Initializes a new instance of <see cref="PostPaymentRequest"/>
        /// </summary>
        public PostPaymentRequest()
        {
        }

        /// <summary>
        /// Gets or sets the card holder's name
        /// </summary>
        [Required]
        [StringLength(30)]
        public string CardHolderName { get; set; }

        /// <summary>
        /// Gets or sets the issuing network
        /// </summary>
        [Required]
        [StringLength(20)]
        public string IssuingNetwork { get; set; }

        /// <summary>
        /// Gets or sets the card number
        /// </summary>
        [Required]
        [StringLength(20)]
        public string CardNumber { get; set; }

        /// <summary>
        /// Gets or sets the expiration date
        /// </summary>
        [Required]
        public DateTime? ExpirationDate { get; set; }

        /// <summary>
        /// Gets or sets the CVV (Card Verification Value)
        /// </summary>
        [Required]
        [StringLength(4)]
        public string Cvv { get; set; }

        /// <summary>
        /// Gets or sets the amount
        /// </summary>
        [Required]
        [Range(0.0, 10000.0)]
        public decimal? Amount { get; set; }
    }
}

Chapter 06 - Online Store Identity

This solution implements Identity Server as authentication and authorization API.

This guide implements in-memory configuration for Identity Server.

This implementation for Identity Server doesn't have any value in real life, if do You want to apply Identity Server in real life, remove in-memory configuration and replace it with database store.

Identity API for Online Store runs on port 56000.

In order to allow connections, We need to add configuration for API resources and clients, this configuration is in Config class:

using System.Collections.Generic;
using System.Security.Claims;
using IdentityModel;
using IdentityServer4.Models;

namespace OnlineStore.API.Identity
{
    public static class Config
    {
        public static IEnumerable<ApiResource> GetApiResources()
            => new List<ApiResource>
            {
                new ApiResource("OnlineStoreAPI", "Online Store API")
                {
                    ApiSecrets =
                    {
                        new Secret("Secret1")
                    }
                }
            };

        public static IEnumerable<Client> GetClients()
            => new List<Client>
            {
                new Client
                {
                    ClientId = "OnlineStoreAPI.Client",
                    AllowedGrantTypes = GrantTypes.ResourceOwnerPassword,
                    ClientSecrets =
                    {
                        new Secret("OnlineStoreAPIClientSecret1".Sha256())
                    },
                    AllowedScopes =
                    {
                        "OnlineStoreAPI"
                    },
                    Claims =
                    {
                        new Claim(JwtClaimTypes.Role, "Administrator"),
                        new Claim(JwtClaimTypes.Role, "Customer"),
                        new Claim(JwtClaimTypes.Role, "WarehouseManager"),
                        new Claim(JwtClaimTypes.Role, "WarehouseOperator")
                    }
                }
            };
    }
}

Also We need to add the configuration for services in Identity Server API Startup class:

using IdentityServer4.Services;
using IdentityServer4.Validation;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using OnlineStore.API.Identity.Domain;
using OnlineStore.API.Identity.Services;
using OnlineStore.API.Identity.Validation;

namespace OnlineStore.API.Identity
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc()
                .SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

            /* Setting up dependency injection */

            // DbContext
            services
                .AddDbContext<IdentityDbContext>(options => options.UseInMemoryDatabase("Identity"));

            // Password validator and profile
            services
                .AddTransient<IResourceOwnerPasswordValidator, ResourceOwnerPasswordValidator>()
                .AddTransient<IProfileService, ProfileService>();

            /* Identity Server */

            services
                .AddIdentityServer()
                .AddDeveloperSigningCredential()
                .AddInMemoryApiResources(Config.GetApiResources())
                .AddInMemoryClients(Config.GetClients());

            services
                .AddAuthentication()
                .AddIdentityServerAuthentication();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
                app.UseDeveloperExceptionPage();

            // Seed IdentityDbContext in-memory

            var authDbContext = app
                .ApplicationServices
                .CreateScope()
                .ServiceProvider
                .GetService<IdentityDbContext>();

            authDbContext.SeedInMemory();

            app.UseIdentityServer();
        }
    }
}

As You know, We're working with in-memory configurations, these configurations apply for DbContext.

To handle authentication and autorization, there are two entities: User and UserClaim.

using Microsoft.EntityFrameworkCore;

namespace OnlineStore.API.Identity.Domain
{
    public class IdentityDbContext : DbContext
    {
        public IdentityDbContext(DbContextOptions<IdentityDbContext> options)
            : base(options)
        {
        }

        public DbSet<User> Users { get; set; }

        public DbSet<UserClaim> UserClaims { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            // Set key for entities

            modelBuilder
                .Entity<User>(builder => builder.HasKey(e => e.UserID));

            modelBuilder
                .Entity<UserClaim>(builder => builder.HasKey(e => e.UserClaimID));

            base.OnModelCreating(modelBuilder);
        }
    }
}

OnlineStore doesn't use Repository and Unit of Work design patterns anymore, the replacement for these design patterns is to have extension methods for DbContext class, later I'll explain this point with examples.

This is the code for AuthDbContextExtentions class:

using System;
using System.Collections.Generic;
using System.Linq;
using IdentityModel;

namespace OnlineStore.API.Identity.Domain
{
    public static class IdentityDbContextExtentions
    {
        public static bool ValidatePassword(this IdentityDbContext dbContext, string userName, string password)
        {
            var user = dbContext.Users.FirstOrDefault(item => item.Email == userName);

            if (user == null)
                return false;

            if (user.Password == password.ToSha256())
                return true;

            return false;
        }

        public static User GetUserByUserName(this IdentityDbContext dbContext, string userName)
            => dbContext.Users.FirstOrDefault(item => item.Email == userName);

        public static User GetUserByID(this IdentityDbContext dbContext, string id)
            => dbContext.Users.FirstOrDefault(item => item.UserID == id);

        public static IEnumerable<UserClaim> GetUserClaimsByUserID(this IdentityDbContext dbContext, string userID)
            => dbContext.UserClaims.Where(item => item.UserID == userID);

        public static void SeedInMemory(this IdentityDbContext dbContext)
        {
            dbContext.Users.Add(new User("1000", "erik.lehnsherr@outlook.com", "magneto".ToSha256(), true));

            dbContext.UserClaims.AddRange(
                new UserClaim(Guid.NewGuid(), "1000", JwtClaimTypes.Subject, "1000"),
                new UserClaim(Guid.NewGuid(), "1000", JwtClaimTypes.PreferredUserName, "eriklehnsherr"),
                new UserClaim(Guid.NewGuid(), "1000", JwtClaimTypes.Role, "Administrator"),
                new UserClaim(Guid.NewGuid(), "1000", JwtClaimTypes.Email, "erik.lehnsherr@outlook.com"),
                new UserClaim(Guid.NewGuid(), "1000", JwtClaimTypes.GivenName, "Erik"),
                new UserClaim(Guid.NewGuid(), "1000", JwtClaimTypes.MiddleName, "M"),
                new UserClaim(Guid.NewGuid(), "1000", JwtClaimTypes.FamilyName, "Lehnsherr")
            );

            dbContext.SaveChanges();

            dbContext.Users.Add(new User("2000", "charlesxavier@gmail.com", "professorx".ToSha256(), true));

            dbContext.UserClaims.AddRange(
                new UserClaim(Guid.NewGuid(), "2000", JwtClaimTypes.Subject, "2000"),
                new UserClaim(Guid.NewGuid(), "2000", JwtClaimTypes.PreferredUserName, "charlesxavier"),
                new UserClaim(Guid.NewGuid(), "2000", JwtClaimTypes.Role, "Administrator"),
                new UserClaim(Guid.NewGuid(), "2000", JwtClaimTypes.Email, "charlesxavier@gmail.com"),
                new UserClaim(Guid.NewGuid(), "2000", JwtClaimTypes.GivenName, "Charles"),
                new UserClaim(Guid.NewGuid(), "2000", JwtClaimTypes.MiddleName, "F"),
                new UserClaim(Guid.NewGuid(), "2000", JwtClaimTypes.FamilyName, "Xavier")
            );

            dbContext.SaveChanges();

            dbContext.Users.Add(new User("3000", "jameslogan@walla.com", "wolverine".ToSha256(), true));

            dbContext.UserClaims.AddRange(
                new UserClaim(Guid.NewGuid(), "3000", JwtClaimTypes.Subject, "3000"),
                new UserClaim(Guid.NewGuid(), "3000", JwtClaimTypes.PreferredUserName, "jameslogan"),
                new UserClaim(Guid.NewGuid(), "3000", JwtClaimTypes.Role, "Customer"),
                new UserClaim(Guid.NewGuid(), "3000", JwtClaimTypes.Email, "jameslogan@walla.com"),
                new UserClaim(Guid.NewGuid(), "3000", JwtClaimTypes.GivenName, "James"),
                new UserClaim(Guid.NewGuid(), "3000", JwtClaimTypes.MiddleName, ""),
                new UserClaim(Guid.NewGuid(), "3000", JwtClaimTypes.FamilyName, "Logan")
            );

            dbContext.SaveChanges();

            dbContext.Users.Add(new User("4000", "ororo_munroe@yahoo.com", "storm".ToSha256(), true));

            dbContext.UserClaims.AddRange(
                new UserClaim(Guid.NewGuid(), "4000", JwtClaimTypes.Subject, "4000"),
                new UserClaim(Guid.NewGuid(), "4000", JwtClaimTypes.PreferredUserName, "ororo_munroe"),
                new UserClaim(Guid.NewGuid(), "4000", JwtClaimTypes.Role, "Customer"),
                new UserClaim(Guid.NewGuid(), "4000", JwtClaimTypes.Email, "ororo_munroe@yahoo.com"),
                new UserClaim(Guid.NewGuid(), "4000", JwtClaimTypes.GivenName, "Ororo"),
                new UserClaim(Guid.NewGuid(), "4000", JwtClaimTypes.MiddleName, ""),
                new UserClaim(Guid.NewGuid(), "4000", JwtClaimTypes.FamilyName, "Munroe")
            );

            dbContext.SaveChanges();

            dbContext.Users.Add(new User("5000", "warehousemanager1@onlinestore.com", "password1".ToSha256(), true));

            dbContext.UserClaims.AddRange(
                new UserClaim(Guid.NewGuid(), "5000", JwtClaimTypes.Subject, "5000"),
                new UserClaim(Guid.NewGuid(), "5000", JwtClaimTypes.PreferredUserName, "warehousemanager1"),
                new UserClaim(Guid.NewGuid(), "5000", JwtClaimTypes.Role, "WarehouseManager"),
                new UserClaim(Guid.NewGuid(), "5000", JwtClaimTypes.Email, "warehousemanager1@onlinestore.com")
            );

            dbContext.SaveChanges();

            dbContext.Users.Add(new User("6000", "warehouseoperator1@onlinestore.com", "password1".ToSha256(), true));

            dbContext.UserClaims.AddRange(
                new UserClaim(Guid.NewGuid(), "6000", JwtClaimTypes.Subject, "6000"),
                new UserClaim(Guid.NewGuid(), "6000", JwtClaimTypes.PreferredUserName, "warehouseoperator1"),
                new UserClaim(Guid.NewGuid(), "6000", JwtClaimTypes.Role, "WarehouseOperator"),
                new UserClaim(Guid.NewGuid(), "6000", JwtClaimTypes.Email, "warehouseoperator1@onlinestore.com")
            );

            dbContext.SaveChanges();
        }
    }
}

All actions in OnlineStore APIs need to get token from Identity API.

Chapter 07 - APIs

There are three projects:

OnlineStore.API.Common
OnlineStore.API.Sales
OnlineStore.API.Warehouse

All of these projects contain a reference to OnlineStore.Core project.

Clients for Payment Gateway

Payment Gateway provides two APIs, one for authentication and other for payment, in order to perform payment requests there are two clients for Rothschild House.

Code for RothschildHouseIdentityClient class:

using System.Net.Http;
using System.Threading.Tasks;
using IdentityModel.Client;
using Microsoft.Extensions.Options;
using OnlineStore.API.Common.Clients.Contracts;

namespace OnlineStore.API.Common.Clients
{
#pragma warning disable CS1591
    public class RothschildHouseIdentityClient : IRothschildHouseIdentityClient
    {
        private readonly RothschildHouseIdentitySettings Settings;

        public RothschildHouseIdentityClient(IOptions<RothschildHouseIdentitySettings> settings)
        {
            Settings = settings.Value;
        }

        public async Task<TokenResponse> GetRothschildHouseTokenAsync()
        {
            using (var client = new HttpClient())
            {
                // todo: Get identity server url from config file

                var disco = await client.GetDiscoveryDocumentAsync(Settings.Url);

                // todo: Get token request from config file

                return await client.RequestPasswordTokenAsync(new PasswordTokenRequest
                {
                    Address = disco.TokenEndpoint,
                    ClientId = Settings.ClientId,
                    ClientSecret = Settings.ClientSecret,
                    UserName = Settings.UserName,
                    Password = Settings.Password
                });
            }
        }
    }
#pragma warning restore CS1591
}

Code for RothschildHousePaymentClient class:

using System.Net.Http;
using System.Threading.Tasks;
using IdentityModel.Client;
using Microsoft.Extensions.Options;
using OnlineStore.API.Common.Clients.Contracts;
using OnlineStore.API.Common.Clients.Models;

namespace OnlineStore.API.Common.Clients
{
#pragma warning disable CS1591
    public class RothschildHousePaymentClient : IRothschildHousePaymentClient
    {
        private readonly RothschildHousePaymentSettings Settings;
        private readonly ApiUrl apiUrl;

        public RothschildHousePaymentClient(IOptions<RothschildHousePaymentSettings> settings)
        {
            Settings = settings.Value;
            apiUrl = new ApiUrl(baseUrl: Settings.Url);
        }

        public async Task<HttpResponseMessage> PostPaymentAsync(TokenResponse token, PostPaymentRequest request)
        {
            using (var client = new HttpClient())
            {
                client.SetBearerToken(token.AccessToken);

                return await client.PostAsync(
                    apiUrl.Controller("Transaction").Action("Payment").ToString(),
                    request.GetStringContent()
                    );
            }
        }
    }
#pragma warning restore CS1591
}

Sales API

Let's take a look on SalesController class:

using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using OnlineStore.API.Common.Clients.Contracts;
using OnlineStore.API.Common.Clients.Models;
using OnlineStore.API.Common.Controllers;
using OnlineStore.API.Common.Filters;
using OnlineStore.API.Common.Responses;
using OnlineStore.API.Sales.Requests;
using OnlineStore.API.Sales.Security;
using OnlineStore.Core.Business.Contracts;

namespace OnlineStore.API.Sales.Controllers
{
#pragma warning disable CS1591
    [Route("api/v1/[controller]")]
    [ApiController]
    public class SalesController : OnlineStoreController
    {
        readonly ILogger Logger;
        readonly IRothschildHouseIdentityClient RothschildHouseIdentityClient;
        readonly IRothschildHousePaymentClient RothschildHousePaymentClient;
        readonly ISalesService SalesService;

        public SalesController(ILogger<SalesController> logger, IRothschildHouseIdentityClient rothschildHouseIdentityClient, IRothschildHousePaymentClient rothschildHousePaymentClient, ISalesService salesService)
            : base()
        {
            Logger = logger;
            RothschildHouseIdentityClient = rothschildHouseIdentityClient;
            RothschildHousePaymentClient = rothschildHousePaymentClient;
            SalesService = salesService;
        }
#pragma warning restore CS1591

        /// <summary>
        /// Retrieves the orders placed by customers
        /// </summary>
        /// <param name="request">Search request</param>
        /// <returns>A sequence of orders</returns>
        /// <response code="200">Returns a list of orders</response>
        /// <response code="401">If client is not authenticated</response>
        /// <response code="403">If client is not autorized</response>
        /// <response code="500">If there was an internal error</response>
        [HttpGet("order")]
        [ProducesResponseType(200)]
        [ProducesResponseType(401)]
        [ProducesResponseType(403)]
        [ProducesResponseType(500)]
        [OnlineStoreActionFilter]
        public async Task<IActionResult> GetOrdersAsync([FromQuery]GetOrdersRequest request)
        {
            Logger?.LogDebug("{0} has been invoked", nameof(GetOrdersAsync));

            // Get response from business logic
            var response = await SalesService
                .GetOrdersAsync(request.PageSize, request.PageNumber, request.OrderStatusID, request.CustomerID, request.EmployeeID, request.ShipperID, request.CurrencyID, request.PaymentMethodID);

            // Return as http response
            return response.ToHttpResult();
        }

        /// <summary>
        /// Retrieves an existing order by id
        /// </summary>
        /// <param name="id">Order ID</param>
        /// <returns>An existing order</returns>
        /// <response code="200">If id exists</response>
        /// <response code="401">If client is not authenticated</response>
        /// <response code="403">If client is not autorized</response>
        /// <response code="404">If id is not exists</response>
        /// <response code="500">If there was an internal error</response>
        [HttpGet("order/{id}")]
        [ProducesResponseType(200)]
        [ProducesResponseType(401)]
        [ProducesResponseType(403)]
        [ProducesResponseType(404)]
        [ProducesResponseType(500)]
        [OnlineStoreActionFilter]
        public async Task<IActionResult> GetOrderAsync(long id)
        {
            Logger?.LogDebug("{0} has been invoked", nameof(GetOrderAsync));

            // Get response from business logic
            var response = await SalesService.GetOrderAsync(id);

            // Return as http response
            return response.ToHttpResult();
        }

        /// <summary>
        /// Retrieves the request model to create a new order
        /// </summary>
        /// <returns>A model that represents the request to create a new order</returns>
        /// <response code="200">Returns the model to create a new order</response>
        /// <response code="401">If client is not authenticated</response>
        /// <response code="403">If client is not autorized</response>
        /// <response code="500">If there was an internal error</response>
        [HttpGet("order-model")]
        [ProducesResponseType(200)]
        [ProducesResponseType(401)]
        [ProducesResponseType(403)]
        [ProducesResponseType(500)]
        [OnlineStoreActionFilter]
        [Authorize(Policy = Policies.CustomerPolicy)]
        public async Task<IActionResult> GetPostOrderModelAsync()
        {
            Logger?.LogDebug("{0} has been invoked", nameof(GetPostOrderModelAsync));

            // Get response from business logic
            var response = await SalesService.GetCreateOrderRequestAsync();

            // Return as http response
            return response.ToHttpResult();
        }

        /// <summary>
        /// Creates a new order
        /// </summary>
        /// <param name="request">Request</param>
        /// <returns>A result that contains the order ID generated by API</returns>
        /// <response code="200">If order was created successfully</response>
        /// <response code="400">If the request is invalid</response>
        /// <response code="401">If client is not authenticated</response>
        /// <response code="403">If client is not autorized</response>
        /// <response code="500">If there was an internal error</response>
        [HttpPost("order")]
        [ProducesResponseType(200)]
        [ProducesResponseType(400)]
        [ProducesResponseType(401)]
        [ProducesResponseType(403)]
        [ProducesResponseType(500)]
        [OnlineStoreActionFilter]
        [Authorize(Policy = Policies.CustomerPolicy)]
        public async Task<IActionResult> PostOrderAsync([FromBody]PostOrderRequest request)
        {
            Logger?.LogDebug("{0} has been invoked", nameof(PostOrderAsync));

            var token = await RothschildHouseIdentityClient
                .GetRothschildHouseTokenAsync();

            if (token.IsError)
                return Unauthorized();

            var paymentRequest = request.GetPostPaymentRequest();

            var paymentHttpResponse = await RothschildHousePaymentClient
                .PostPaymentAsync(token, paymentRequest);

            if (!paymentHttpResponse.IsSuccessStatusCode)
                return BadRequest();

            var paymentResponse = await paymentHttpResponse
                .GetPaymentResponseAsync();

            var entity = request.GetHeader();

            entity.CreationUser = UserInfo.UserName;

            // Get response from business logic
            var response = await SalesService
                .CreateOrderAsync(entity, request.GetDetails().ToArray());

            // Return as http response
            return response.ToHttpResult();
        }

        /// <summary>
        /// Creates a new order model from existing order
        /// </summary>
        /// <param name="id">Order ID</param>
        /// <returns>A model for a new order</returns>
        /// <response code="200">If order was cloned successfully</response>
        /// <response code="401">If client is not authenticated</response>
        /// <response code="403">If client is not autorized</response>
        /// <response code="404">If id is not exists</response>
        /// <response code="500">If there was an internal error</response>
        [HttpGet("order/{id}/clone")]
        [ProducesResponseType(200)]
        [ProducesResponseType(401)]
        [ProducesResponseType(403)]
        [ProducesResponseType(500)]
        [OnlineStoreActionFilter]
        [Authorize(Policy = Policies.CustomerPolicy)]
        public async Task<IActionResult> CloneOrderAsync(int id)
        {
            Logger?.LogDebug("{0} has been invoked", nameof(CloneOrderAsync));

            // Get response from business logic
            var response = await SalesService.CloneOrderAsync(id);

            // Return as http response
            return response.ToHttpResult();
        }

        /// <summary>
        /// Cancels an existing order
        /// </summary>
        /// <param name="id">ID for order</param>
        /// <returns>A success response if order is cancelled</returns>
        /// <response code="200">If order was cancelled successfully</response>
        /// <response code="401">If client is not authenticated</response>
        /// <response code="403">If client is not autorized</response>
        /// <response code="404">If id is not exists</response>
        /// <response code="500">If there was an internal error</response>
        [HttpDelete("order/{id}")]
        [ProducesResponseType(200)]
        [ProducesResponseType(401)]
        [ProducesResponseType(403)]
        [ProducesResponseType(404)]
        [ProducesResponseType(500)]
        [OnlineStoreActionFilter]
        [Authorize(Policy = Policies.CustomerPolicy)]
        public async Task<IActionResult> DeleteOrderAsync(int id)
        {
            Logger?.LogDebug("{0} has been invoked", nameof(DeleteOrderAsync));

            // Get response from business logic
            var response = await SalesService.CancelOrderAsync(id);

            // Return as http response
            return response.ToHttpResult();
        }
    }
}

ViewModel versus Request

ViewModel is an object that contains behavior, request is the action related to invoke a Web API method, this is the misunderstood: ViewModel is an object linked to a view, contains behavior to handle changes and sync up with view; usually the parameter for Web API method is an object with properties, so this definition is named Request; MVC is not MVVM, the life's cycle for model is different in those patterns, this definition doesn't keep state between UI and API, also the process to set properties values in request from query string is handled by a model binder.

Settings

To provide settings for API, first We need to define configurations in appsettings.json file:

{
  "Logging": {
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "OnlineStore": "server=(local);database=OnlineStore;integrated security=yes;MultipleActiveResultSets=True;"
  },
  "IdentityServerSettings": {
    "Authority": "http://localhost:5100",
    "RequireHttpsMetadata": false,
    "ApiName": "OnlineStoreAPI",
    "ApiSecret": "Secret1"
  },
  "OnlineStoreIdentityClientSettings": {
    "Url": "http://localhost:5100",
    "ClientId": "OnlineStoreAPI.Client",
    "ClientSecret": "OnlineStoreAPIClientSecret1",
    "UserName": "",
    "Password": ""
  },
  "RothschildHouseIdentitySettings": {
    "Url": "http://localhost:18000",
    "ClientId": "onlinestoreclient",
    "ClientSecret": "onlinestoreclientsecret1",
    "UserName": "administrator@onlinestore.com",
    "Password": "onlinestore1"
  },
  "RothschildHousePaymentSettings": {
    "Url": "http://localhost:19000"
  }
}

Then take a look on Startup.cs class:

using System;
using System.IO;
using System.Reflection;
using IdentityServer4.AccessTokenValidation;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;
using OnlineStore.API.Common.Clients;
using OnlineStore.API.Common.Clients.Contracts;
using OnlineStore.API.Sales.PolicyRequirements;
using OnlineStore.API.Sales.Security;
using OnlineStore.Core;
using OnlineStore.Core.Business;
using OnlineStore.Core.Business.Contracts;
using OnlineStore.Core.Domain;
using Swashbuckle.AspNetCore.Swagger;

namespace OnlineStore.API.Sales
{
#pragma warning disable CS1591
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            /* Configuration for MVC */

            services
                .AddMvc()
                .SetCompatibilityVersion(CompatibilityVersion.Version_2_2)
                .AddJsonOptions(options =>
                {
                    options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
                });

            /* Setting dependency injection */

            // For DbContext
            services.AddDbContext<OnlineStoreDbContext>(builder =>builder.UseSqlServer(Configuration["ConnectionStrings:OnlineStore"]));

            // User info
            services.AddScoped<IUserInfo, UserInfo>();

            // Logger for services
            services.AddScoped<ILogger, Logger<Service>>();

            /* Rothschild House Payment gateway */
            services.Configure<RothschildHouseIdentitySettings>(Configuration.GetSection("RothschildHouseIdentitySettings"));
            services.AddSingleton<RothschildHouseIdentitySettings>();

            services.Configure<RothschildHousePaymentSettings>(Configuration.GetSection("RothschildHousePaymentSettings"));
            services.AddSingleton<RothschildHousePaymentSettings>();

            services.AddScoped<IRothschildHouseIdentityClient, RothschildHouseIdentityClient>();
            services.AddScoped<IRothschildHousePaymentClient, RothschildHousePaymentClient>();

            /* Online Store Services */
            services.AddScoped<ISalesService, SalesService>();

            /* Configuration for authorization */

            services
                .AddMvcCore()
                .AddAuthorization(options =>
                {
                    options.AddPolicy(Policies.CustomerPolicy, builder =>
                    {
                        builder.Requirements.Add(new CustomerPolicyRequirement());
                    });
                });

            /* Configuration for Identity Server authentication */

            services
                .AddAuthentication("Bearer")
                .AddIdentityServerAuthentication(options =>
                {
                    var settings = new IdentityServerAuthenticationOptions();

                    Configuration.Bind("IdentityServerSettings", settings);

                    options.Authority = settings.Authority;
                    options.RequireHttpsMetadata = settings.RequireHttpsMetadata;
                    options.ApiName = settings.ApiName;
                    options.ApiSecret = settings.ApiSecret;
                });

            /* Configuration for Help page */

            services.AddSwaggerGen(options =>
            {
                options.SwaggerDoc("v1", new Info { Title = "Online Store Sales API", Version = "v1" });

                // Get xml comments path
                var xmlFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.xml";
                var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);

                // Set xml path
                options.IncludeXmlComments(xmlPath);
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseCors(builder =>
            {
                // Add client origin in CORS policy

                // todo: Set port number for client app from appsettings file

                builder
                    .WithOrigins("http://localhost:4200")
                    .AllowAnyHeader()
                    .AllowAnyMethod()
                ;
            });

            /* Use authentication for Web API */

            app.UseAuthentication();

            /* Configuration for Swagger */

            app.UseSwagger();

            app.UseSwaggerUI(options => options.SwaggerEndpoint("/swagger/v1/swagger.json", "Online Store Sales API"));

            app.UseMvc();
        }
    }
#pragma warning restore CS1591
}

This class it's the configuration point for Web API project, in this class there is the configuration for dependency injection, API's configuration and another settings.

For API project, these are the routes for controllers:

Verb	Route	Description
GET	api/v1/Sales/order	Gets orders
GET	api/v1/Sales/order/5	Gets an order by id
GET	api/v1/Sales/order-model	Gets model to create order
GET	api/v1/Sales/order/5/clone	Clones an existing order
POST	api/v1/Sales/order	Creates a new order
DELETE	api/v1/Sales/order/5	Deletes an existing order

There is a v1 in each route, this is because the version for API is 1 and that value is defined in Route attribute for controllers in API project.

Chapter 08 - Help Page for API

API uses Swagger to show a help page.

The following package is required to show a help page with Swagger:

Swashbuckle.AspNetCore

The configuration for Swagger is located in Startup class, addition for Swagger is in ConfigureServices method:

/* Configuration for Help page */

services.AddSwaggerGen(options =>
{
    options.SwaggerDoc("v1", new Info { Title = "Online Store Sales API", Version = "v1" });

    // Get xml comments path
    var xmlFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.xml";
    var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);

    // Set xml path
    options.IncludeXmlComments(xmlPath);
});

The configuration for endpoint is in Configure method:

/* Configuration for Swagger */

app.UseSwagger();

app.UseSwaggerUI(options => options.SwaggerEndpoint("/swagger/v1/swagger.json", "Online Store Sales API"));

Swagger allows to show description for actions in controllers, these descriptions are taken from xml comments.

Help Page:

Help Page For Web API

Models Section in Help Page:

Models Section In Help Page For Web API

Help Page for API it's a good practice, because provides information about API for clients.

Chapter 09 - Unit Tests for API

Now We proceed to explain unit tests for API project, these tests work with in-memory database, what is the difference between unit tests and integration tests? for unit tests We simulate all dependencies for Web API project and for integration tests We run a process that simulates Web API execution. I mean a simulation of Web API (accept Http requests), obviously there is more information about unit tests and integration tests but at this point this basic idea is enough.

What is TDD? Testing is important in these days, because with unit tests it's easy to performing tests for features before to publish, Test Driven Development is the way to define tests and validate the behavior in code.

Another concept linked to TDD is AAA: Arrange, Act and Assert is a pattern for arranging and formatting code in test methods.

Arrange: is the block for creation of objects
Act: is the block to place all invocations for methods
Assert: is the block to validate the results from methods invocation

Let's take a look for SalesControllerTests class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using OnlineStore.API.Common.UnitTests.Mocks;
using OnlineStore.API.Sales.Controllers;
using OnlineStore.API.Sales.Requests;
using OnlineStore.API.Sales.UnitTests.Mocks;
using OnlineStore.Core.Business.Requests;
using OnlineStore.Core.Business.Responses;
using OnlineStore.Core.Domain.Sales;
using Xunit;

namespace OnlineStore.API.Sales.UnitTests
{
    public class SalesControllerTests
    {
        [Fact]
        public async Task TestSearchOrdersAsync()
        {
            // Arrange
            var userInfo = IdentityMocker.GetCustomerIdentity().GetUserInfo();
            var service = ServiceMocker.GetSalesService(userInfo, nameof(TestSearchOrdersAsync), true);
            var controller = new SalesController(null, null, null, service);
            var request = new GetOrdersRequest();

            // Act
            var response = await controller.GetOrdersAsync(request) as ObjectResult;
            var value = response.Value as IPagedResponse<OrderInfo>;

            // Assert
            Assert.False(value.DidError);
        }

        [Fact]
        public async Task TestSearchOrdersByCurrencyAsync()
        {
            // Arrange
            var userInfo = IdentityMocker.GetCustomerIdentity().GetUserInfo();
            var service = ServiceMocker.GetSalesService(userInfo, nameof(TestSearchOrdersByCurrencyAsync), true);
            var controller = new SalesController(null, null, null, service);
            var request = new GetOrdersRequest
            {
                CurrencyID = "USD"
            };

            // Act
            var response = await controller.GetOrdersAsync(request) as ObjectResult;
            var value = response.Value as IPagedResponse<OrderInfo>;

            // Assert
            Assert.False(value.DidError);
            Assert.True(value.Model.Count(item => item.CurrencyID == request.CurrencyID) == value.Model.Count());
        }

        [Fact]
        public async Task TestSearchOrdersByCustomerAsync()
        {
            // Arrange
            var userInfo = IdentityMocker.GetCustomerIdentity().GetUserInfo();
            var service = ServiceMocker.GetSalesService(userInfo, nameof(TestSearchOrdersByCustomerAsync), true);
            var controller = new SalesController(null, null, null, service);
            var request = new GetOrdersRequest
            {
                CustomerID = 1
            };

            // Act
            var response = await controller.GetOrdersAsync(request) as ObjectResult;
            var value = response.Value as IPagedResponse<OrderInfo>;

            // Assert
            Assert.False(value.DidError);
            Assert.True(value.Model.Count(item => item.CustomerID == request.CustomerID) == value.Model.Count());
        }

        [Fact]
        public async Task TestSearchOrdersByEmployeeAsync()
        {
            // Arrange
            var userInfo = IdentityMocker.GetCustomerIdentity().GetUserInfo();
            var service = ServiceMocker.GetSalesService(userInfo, nameof(TestSearchOrdersByEmployeeAsync), true);
            var controller = new SalesController(null, null, null, service);
            var request = new GetOrdersRequest
            {
                EmployeeID = 1
            };

            // Act
            var response = await controller.GetOrdersAsync(request) as ObjectResult;
            var value = response.Value as IPagedResponse<OrderInfo>;

            // Assert
            Assert.False(value.DidError);
            Assert.True(value.Model.Count(item => item.EmployeeID == request.EmployeeID) == value.Model.Count());
        }

        [Fact]
        public async Task TestGetOrderAsync()
        {
            // Arrange
            var userInfo = IdentityMocker.GetCustomerIdentity().GetUserInfo();
            var service = ServiceMocker.GetSalesService(userInfo, nameof(TestGetOrderAsync), true);
            var controller = new SalesController(null, null, null, service);
            var id = 1;

            // Act
            var response = await controller.GetOrderAsync(id) as ObjectResult;
            var value = response.Value as ISingleResponse<OrderHeader>;

            // Assert
            Assert.False(value.DidError);
        }

        [Fact]
        public async Task TestGetNonExistingOrderAsync()
        {
            // Arrange
            var userInfo = IdentityMocker.GetCustomerIdentity().GetUserInfo();
            var service = ServiceMocker.GetSalesService(userInfo, nameof(TestGetNonExistingOrderAsync), true);
            var controller = new SalesController(null, null, null, service);
            var id = 0;

            // Act
            var response = await controller.GetOrderAsync(id) as ObjectResult;
            var value = response.Value as ISingleResponse<OrderHeader>;

            // Assert
            Assert.False(value.DidError);
        }

        [Fact]
        public async Task TestGetCreateOrderRequestAsync()
        {
            // Arrange
            var userInfo = IdentityMocker.GetCustomerIdentity().GetUserInfo();
            var service = ServiceMocker.GetSalesService(userInfo, nameof(TestGetCreateOrderRequestAsync), true);
            var controller = new SalesController(null, null, null, service);

            // Act
            var response = await controller.GetPostOrderModelAsync() as ObjectResult;
            var value = response.Value as ISingleResponse<CreateOrderRequest>;

            // Assert
            Assert.False(value.DidError);
        }

        [Fact]
        public async Task TestPostOrderAsync()
        {
            // Arrange
            var userInfo = IdentityMocker.GetCustomerIdentity().GetUserInfo();
            var service = ServiceMocker.GetSalesService(userInfo, nameof(TestPostOrderAsync), true);
            var identityClient = new MockedRothschildHouseIdentityClient();
            var paymentClient = new MockedRothschildHousePaymentClient();
            var controller = new SalesController(null, identityClient, paymentClient, service);
            var request = new PostOrderRequest
            {
                ID = 2,
                CustomerID = 1,
                PaymentMethodID = new Guid("7671A4F7-A735-4CB7-AAB4-CF47AE20171D"),
                CurrencyID = "USD",
                Comments = "Order from unit tests",
                Details = new List<OrderDetailRequest>
                {
                    new OrderDetailRequest
                    {
                        ID = 2,
                        ProductID = 1,
                        Quantity = 1
                    }
                }
            };

            // Act
            var response = await controller.PostOrderAsync(request) as ObjectResult;
            var value = response.Value as ISingleResponse<OrderHeader>;

            // Assert
            Assert.False(value.DidError);
            Assert.True(value.Model.ID.HasValue);
        }

        [Fact]
        public async Task TestCloneOrderAsync()
        {
            // Arrange
            var userInfo = IdentityMocker.GetCustomerIdentity().GetUserInfo();
            var service = ServiceMocker.GetSalesService(userInfo, nameof(TestCloneOrderAsync), true);
            var controller = new SalesController(null, null, null, service);
            var id = 1;

            // Act
            var response = await controller.CloneOrderAsync(id) as ObjectResult;
            var value = response.Value as ISingleResponse<OrderHeader>;

            // Assert
            Assert.False(value.DidError);
        }
    }
}

IdentityMocker class provides user identities, GetUserInfo extension method returns an implementation of IUserInfo interface that contains information for authenticated user.

Chapter 10 - Integration Tests for API

As We did with unit tests, integration tests should be created according to Web API, so let's choose SalesController to explain the model for integration tests.

Now, this is the code for SalesTests class:

using System;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using OnlineStore.API.Common.IntegrationTests;
using OnlineStore.API.Common.IntegrationTests.Helpers;
using Xunit;

namespace OnlineStore.API.Sales.IntegrationTests
{
    public class SalesTests : IClassFixture<TestFixture<Startup>>
    {
        readonly HttpClient Client;

        public SalesTests(TestFixture<Startup> fixture)
        {
            Client = fixture.Client;
        }

        [Fact]
        public async Task GetOrdersAsCustomerAsync()
        {
            // Arrange
            var token = await TokenHelper.GetTokenForWolverineAsync();
            var request = new
            {
                Url = "/api/v1/Sales/order?pageSize=10&pageNumber=1"
            };

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client.GetAsync(request.Url);

            var content = await response.Content.ReadAsStringAsync();

            // Assert
            response.EnsureSuccessStatusCode();
        }

        [Fact]
        public async Task GetOrdersByCurrencyAsCustomerAsync()
        {
            // Arrange
            var token = await TokenHelper.GetTokenForWolverineAsync();
            var request = new
            {
                Url = "/api/v1/Sales/order?pageSize=10&pageNumber=1¤cyID=1"
            };

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client.GetAsync(request.Url);

            // Assert
            response.EnsureSuccessStatusCode();
        }

        [Fact]
        public async Task SearchOrdersByCustomerAsCustomerAsync()
        {
            // Arrange
            var token = await TokenHelper.GetTokenForWolverineAsync();
            var request = new
            {
                Url = "/api/v1/Sales/order"
            };

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client.GetAsync(request.Url);

            // Assert
            response.EnsureSuccessStatusCode();
        }

        [Fact]
        public async Task GetOrdersByEmployeeAsCustomerAsync()
        {
            // Arrange
            var token = await TokenHelper.GetTokenForWolverineAsync();
            var request = new
            {
                Url = "/api/v1/Sales/order?employeeId=1"
            };

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client.GetAsync(request.Url);

            // Assert
            response.EnsureSuccessStatusCode();
        }

        [Fact]
        public async Task GetOrderByIdAsCustomerAsync()
        {
            // Arrange
            var token = await TokenHelper.GetTokenForWolverineAsync();
            var request = new
            {
                Url = "/api/v1/Sales/order/1"
            };

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client.GetAsync(request.Url);

            // Assert
            response.EnsureSuccessStatusCode();
        }

        [Fact]
        public async Task GetOrderByNonExistingIdAsCustomerAsync()
        {
            // Arrange
            var token = await TokenHelper.GetTokenForWolverineAsync();
            var request = new
            {
                Url = "/api/v1/Sales/order/0"
            };

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client.GetAsync(request.Url);

            // Assert
            Assert.True(response.StatusCode == HttpStatusCode.NotFound);
        }

        [Fact]
        public async Task GetPostOrderRequestAsCustomerAsync()
        {
            // Arrange
            var token = await TokenHelper.GetTokenForWolverineAsync();
            var request = new
            {
                Url = "/api/v1/Sales/order-model"
            };

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client.GetAsync(request.Url);

            // Assert
            response.EnsureSuccessStatusCode();
        }

        [Fact]
        public async Task GetPlaceOrderRequestAsWarehouseOperatorAsync()
        {
            // Arrange
            var token = await TokenHelper.GetTokenForWarehouseOperatorAsync();
            var request = new
            {
                Url = "/api/v1/Sales/order-model"
            };

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client.GetAsync(request.Url);

            // Assert
            Assert.True(response.StatusCode == HttpStatusCode.Forbidden);
        }

        [Fact]
        public async Task PlaceOrderAsCustomerAsync()
        {
            // Arrange
            var request = new
            {
                Url = "/api/v1/Sales/order",
                Body = new
                {
                    UserName = "jameslogan@walla.com",
                    Password = "wolverine",
                    CardHolderName = "James Logan",
                    IssuingNetwork = "Visa",
                    CardNumber = "4024007164051145",
                    ExpirationDate = new DateTime(2024, 6, 1),
                    Cvv = "987",
                    Total = 29.99m,
                    CustomerID = 1,
                    CurrencyID = "USD",
                    PaymentMethodID = new Guid("7671A4F7-A735-4CB7-AAB4-CF47AE20171D"),
                    Comments = "Order from integration tests",
                    Details = new[]
                    {
                        new
                        {
                            ProductID = 1,
                            Quantity = 1
                        }
                    }
                }
            };

            var token = await TokenHelper
                .GetOnlineStoreTokenAsync(request.Body.UserName, request.Body.Password);

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client
                .PostAsync(request.Url, ContentHelper.GetStringContent(request.Body));

            // Assert
            response.EnsureSuccessStatusCode();
        }

        [Fact]
        public async Task CloneOrderAsCustomerAsync()
        {
            // Arrange
            var token = await TokenHelper.GetTokenForWolverineAsync();
            var request = new
            {
                Url = "/api/v1/Sales/order/1/clone"
            };

            // Act
            Client.SetBearerToken(token.AccessToken);

            var response = await Client.GetAsync(request.Url);

            // Assert
            response.EnsureSuccessStatusCode();
        }
    }
}

IdentityServerHelper class provides static methods to retrieve valid tokens.

SetBearerToken is an extension method that allows to set an authorization header with a bearer token.

As We can see those methods perform tests for Urls in Web API project, please note that all tests are async methods.

Don't forget We can have more tests, We have another project to have tests for Warehouse API.

To run integration tests, We need to run the following APIs: payment gateway, identity and Online store APIs.

In order to work with integration tests, We need to create a class to provide a Web Host to performing Http behavior, this class it will be TestFixture and to represent Http requests for Web API, there is a class with name SalesTests, this class will contains all requests for defined actions in SalesController class, but using a mocked Http client.

Code for TestFixture class:

using System;
using System.IO;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Reflection;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc.ApplicationParts;
using Microsoft.AspNetCore.Mvc.Controllers;
using Microsoft.AspNetCore.Mvc.ViewComponents;
using Microsoft.AspNetCore.TestHost;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace OnlineStore.API.Common.IntegrationTests
{
    public class TestFixture<TStartup> : IDisposable
    {
        public static string GetProjectPath(string projectRelativePath, Assembly startupAssembly)
        {
            var projectName = startupAssembly.GetName().Name;

            var applicationBasePath = AppContext.BaseDirectory;

            var directoryInfo = new DirectoryInfo(applicationBasePath);

            do
            {
                directoryInfo = directoryInfo.Parent;

                var projectDirectoryInfo = new DirectoryInfo(Path.Combine(directoryInfo.FullName, projectRelativePath));

                if (projectDirectoryInfo.Exists)
                    if (new FileInfo(Path.Combine(projectDirectoryInfo.FullName, projectName, $"{projectName}.csproj")).Exists)
                        return Path.Combine(projectDirectoryInfo.FullName, projectName);
            }
            while (directoryInfo.Parent != null);

            throw new Exception($"Project root could not be located using the application root {applicationBasePath}.");
        }

        private TestServer Server;

        public TestFixture()
            : this(Path.Combine(""))
        {
        }

        public HttpClient Client { get; }

        public void Dispose()
        {
            Client.Dispose();
            Server.Dispose();
        }

        protected virtual void InitializeServices(IServiceCollection services)
        {
            var startupAssembly = typeof(TStartup).GetTypeInfo().Assembly;

            var manager = new ApplicationPartManager
            {
                ApplicationParts =
                {
                    new AssemblyPart(startupAssembly)
                },
                FeatureProviders =
                {
                    new ControllerFeatureProvider(),
                    new ViewComponentFeatureProvider()
                }
            };

            services.AddSingleton(manager);
        }

        protected TestFixture(string relativeTargetProjectParentDir)
        {
            var startupAssembly = typeof(TStartup).GetTypeInfo().Assembly;
            var contentRoot = GetProjectPath(relativeTargetProjectParentDir, startupAssembly);

            var configurationBuilder = new ConfigurationBuilder()
                .SetBasePath(contentRoot)
                .AddJsonFile("appsettings.json");

            var webHostBuilder = new WebHostBuilder()
                .UseContentRoot(contentRoot)
                .ConfigureServices(InitializeServices)
                .UseConfiguration(configurationBuilder.Build())
                .UseEnvironment("Development")
                .UseStartup(typeof(TStartup));

            // Create instance of test server
            Server = new TestServer(webHostBuilder);

            // Add configuration for client
            Client = Server.CreateClient();

            Client.BaseAddress = new Uri("http://localhost:5001");

            Client.DefaultRequestHeaders.Accept.Clear();
            Client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        }
    }
}

Code Improvements

Save logs to text file
Implement Money Pattern to represent money in application
Add a section to explain why this solution doesn't implement Repository and Unit of Work design patterns

Points of Interest

In this article, We're working with Entity Framework Core.
Entity Framework Core has in-memory database.
Extension methods for OnLineStoreDbContext class allow to us expose specific operations, in some cases We don't want to have GetAll, Add, Update or Remove operations.
Help page for Web API has been built with Swagger.
Unit tests perform testing for Assemblies.
Integration tests perform testing for Web Server.
Unit and integration tests have been built with xUnit framework.
Mocker is an object that creates an instance of object in testing.

History

12^th December, 2016: Initial version
13^th December, 2016: Addition of Business Layer
15^th December, 2016: Addition of Mocker
31^th December, 2016: Addition of Web API
5^th January, 2017: Addition of Unit Tests for Web API
22^th January, 2017: Addition of Change Log
4^th February, 2017: Addition of Async Operations
15^th May, 2017: Addition of Logs
29^th October, 2017: Code Refactor, using of Service in Business Layer
10^th February, 2018: Addition of exclusions for Change Log
28^th May, 2018: Addition of Integration Tests for Web API
2^nd October, 2018: Addition of in memory database for Unit Tests
25^th November, 2018: Addition of Help Page for Web API
27^th November, 2018: Addition of Related Links section
16^th January, 2019: Addition of Identity Server
23^th January, 2019: Addition of Payment Gateway
10^th February, 2019: Addition of Clients for Payment Gateway
9^th February, 2020: Addition of microservices architecture

Entity Framework Core 2 for the Enterprise

Introduction

Payment Gateway

Running Payment Gateway

Credentials for Online Store

Payment Schema

Payment Data

Background

Architecture: Big Picture

Prerequisites

Skills

Software

Table of Contents

Using the Code

Chapter 01 - Database

Tables

Chapter 02 - Core Project

Domain

Keys

Data Layer

Naming Issue

Stored Procedures versus LINQ Queries

Change Tracking

Business

Naming Issue

Business Layer: Handle Related Aspects To Business

Chapter 03 - Putting All Code Together

Get All

Get by Key

Chapter 04 - Mocker

Chapter 05 - Payment Gateway

RothschildHouse.IdentityServer

RothschildHouse

Chapter 06 - Online Store Identity

Chapter 07 - APIs

Clients for Payment Gateway

Sales API

Settings

Chapter 08 - Help Page for API

Chapter 09 - Unit Tests for API

Chapter 10 - Integration Tests for API

Code Improvements

Related Links

Points of Interest

History