Introduction
In this article we will learn to implement 3- Tier
architecture in C#.NET application. 3-Tier
architecture is very famous and well known buzz word in world of software
development. If we analyze any traditional project then we will find that most
of (at least 60-70 %) them has traditional N-Tier, basically 3-Tier
architecture. It does not matter whether it is web or windows application, we
can implement 3-Tier architecture in any type of environment.
Although it is very well known and common architecture but
it’s not very clear to fresher developer or those who are very new in project
development.
Why 3-Tier
Architecture?
Still I can remember that, the first organization in my
career was dealing with one small POS (Point of Sell) project. It was a windows application and there was no
layered architecture. We coder people started to write all codes in behind of windows
form. Problem started after few days.
How? When our manager announced that we have to develop one web version of same
product. Again we started to develop web pages from scratch and started to write
all code. Totally mess.
So, this is the problem and the solution is tired
architecture. If we separate our codes by layer then changes in one layer will
not affect much to another one. Tomorrow
if business demands, we can change UI very quickly by using existing code.
Difference between Tier and Layer
It is one confusing question for beginner. Few think that
both are same. But they are not same. Tier represents different hardware box.
Means the components are physically separated to different machines. But in
case of layer all component remains in same system.
What are the Layers?
Theoretically it is N-Tier architecture. So, we can create
as much layer as possible but basically people classify code in three different
categories and put them in three different layers. So, for this article we will
consider N-Tier architecture as 3-Tier architecture and try to implement one
sample application.
Let’s discuss each and every Layer at first.
Presentation Layer/ UI
Layer
This is the top most layer of application where user
performs their activity. Let’s take example of any application where user needs
to fill up one form. This form is
nothing nut presentation layer. In windows application windows form is
presentation layer and in web application web form belongs to presentation
layer. Basically user’s input validation and rule processing performs in this
layer.
Business Layer
This is on top of presentation layer. As the name suggest,
most of the business operation performs here. For example, after collecting
form data we want to validate them with our custom business rule. Basically we define classes and business
entities in this layer.
Data Access Layer
It is on top of Business Logic Layer Data Access Layer
presents. It contains methods that helps business layer to connect with
database and perform CRUD operation. In data access layer generally all
database related code and stuff belongs to. Sometimes people use platform
independent data access layer to fetch data from different database vendor.
Let’s Implement
Before start with example one more question need to be
clear. How we will pass data from one layer to another layer? Means in which
form data from pass?
There are many solutions for this problem. For our example
we will pass data through function parameter. In this example we will implement
one small windows application to fetch data from database using 3-Tier
architecture. In this example we will
read data from single "Person" Table.
Code for Data Access Layer
Let’s start from Data access layer; we will create function
to read data from database. Have a look
on below code.
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
namespace WindowsFormsApplication1.DAL
{
public class PersonDAL
{
public string ConString =
"Data Source=SOURAV-PC\\SQL_INSTANCE;Initial Catalog=test;Integrated Security=True";
SqlConnection con = new SqlConnection();
DataTable dt = new DataTable();
public DataTable Read()
{
con.ConnectionString = ConString;
if (ConnectionState.Closed == con.State)
con.Open();
SqlCommand cmd = new SqlCommand("select * from Person",con);
try
{
SqlDataReader rd = cmd.ExecuteReader();
dt.Load(rd);
return dt;
}
catch
{
throw;
}
}
public DataTable Read(Int16 Id)
{
con.ConnectionString = ConString;
if (ConnectionState.Closed == con.State)
con.Open();
SqlCommand cmd = new SqlCommand("select * from Person where ID= "+ Id +"", con);
try
{
SqlDataReader rd = cmd.ExecuteReader();
dt.Load(rd);
return dt;
}
catch
{
throw;
}
}
}
}
We have created two overloaded function to read data. One
function will not take any argument and other function will fetch data using
ID.
Create Business Logic
Layer
Now, we will create Business Logic Layer to communicate with
both Presentation layer and Data access layer. Here is our code for Business
layer.
using System; using System.Collections.Generic; using System.Data; using WindowsFormsApplication1.DAL;
namespace WindowsFormsApplication1.BLL
{
public class PersonBLL
{
public DataTable GetPersons()
{
try
{
PersonDAL objdal = new PersonDAL();
return objdal.Read();
}
catch
{
throw;
}
}
public DataTable GetPersons(Int16 ID)
{
try
{
PersonDAL objdal = new PersonDAL();
return objdal.Read(ID);
}
catch
{
throw;
}
}
}
}
Create Presentation
Layer.
This is the top most layer where user will interact with
system. We will create simple windows for like below.
The form contains one datagrid one textbox and one button.
In load event of form we will pull all data and it will show in datagrid. There
is another operation, where user can able to fetch particular person by
providing person ID. Have a look on below code.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using WindowsFormsApplication1.BLL;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
try
{
PersonBLL p = new PersonBLL();
this.dataGridView1.DataSource = p.GetPersons(Convert.ToInt16(this.txtID.Text));
}
catch
{
MessageBox.Show("Error Occurred");
}
}
private void Form1_Load(object sender, EventArgs e)
{
try
{
PersonBLL p = new PersonBLL();
this.dataGridView1.DataSource = p.GetPersons();
}
catch
{
MessageBox.Show("Error Occurred");
}
}
}
}
Folder structure in solution explorer
Here is our sample folder stricture in solution explorer. We have created all layers in same solution. You may create separate solution for each layer.
Here is sample output in form load event.
If we want to search particular person, we have to provide
ID.
Table Stricture
Here is our table structure. It contains three fields ID,
name and surname.
Table Name:-Person
Conclusion
In this article we have discussed how to implement simple 3-tier architecture in C# application. Hope you have understood the concept.
I am software developer from INDIA. Beside my day to day development work, i like to learn new technologies to update myself. I am passionate blogger and author in various technical community including dotnetfunda.com , c-sharpcorner.com and codeproject. My area of interest is modern web technology in Microsoft stack. Visit to my personal blog here.
http://ctrlcvprogrammer.blogspot.in/