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11 votes for this article.

Popularity: 4.47 Rating: 4.30 out of 5

Introduction

I've decided to write this article for two reasons: first, my enthusiasm with the Monorail framework, and second, the .Net community has displayed a growing interest on MVC as an alternative to traditional WebForm applications, not only because of Monorail, but also due to the arising of the new ASP.NET MVC framework.

The MVC Pattern

MVC is the acronym for Model-View-Controller, a design pattern that enforces the separation of concerns on the presentation layer. Note that MVC is in no way limited to web applications, it might also be applied to other platforms that expose a presentation layer, e.g. a desktop environment.

MVC enables the decoupling of data access logic (model) from user interface logic (view), and establishing the controller as an intermediate component.

Model: Represents the domain, that is, the entities that encapsulate raw data plus the domain logic. Note that the MVC pattern doesn't mention how the data persistence should be implemented. Usually it is encapsulated by the Model component.

View: This is the user interface components. They know how to present data, and expose graphic elements such as buttons, list and text boxes, that allow user interaction.

Controller: The controller is the component that orders the rendering of the view, responds to events of the user interface and invokes changes in the model.

Although some authors conclude that WebForms implement the MVC pattern, it must be said that in WebForms, the controller rule is shared between the aspx file, the code behind and the web controls, which goes against the separation of concerns and the single responsibility principle.

The Monorail Framework

Monorail, developed by Castle Project since 2003, is an open source MVC framework for .Net web applications, inspired on Ruby on Rails Action Pack. The Monorail flow could be described in a few lines, but since a picture is worth 10,000 words...

Note that Monorail has an implementation of IHttpHandler, so it still takes advantage of Asp.Net infrastructure (e.g.: session management, events and security).

Having said that, we can enumerate some advantages of Monorail over traditional WebForm applications:

Unlike WebForms, Monorail doesn't have a complex page life cycle.

In Monorail, the separation of concerns principle is enforced. When you develop your Monorail app, you naturally think of it as a structure of models, views and controllers. In WebForms, on the other hand, the designer hides the relationship of these structures from the developer, often resulting in a bad practice of mixing view code and controller code. Monorail doesn't have a designer, so you must write your views manually. It might be considered a bad thing, that's true, but you have total control over how your html is written. In WebForms, on the other hand, the designer often messes up your html code, and even introduces unneeded code.

With Monorail, one doesn't have to be concerned with view state. Although HTTP is stateless by nature, with WebForms Microsoft has introduced the idea of a view state, maintaining the view data through page's life cycle. This is good, but adds too much complexity to the development and decreases overall performance, and introduces security issues.

Monorail allows unit testing over controllers, due to the decoupled design. On the other hand, WebForms design makes it dificult to perform unit testing on the code behind.

Monorail Hands-On: The Northwind Traders Sample Application

The goal of Northwind Traders application is to provide simple CRUD functionalities for Products and Suppliers of the company. That is, we must be able to create, retrieve, update and delete products and suppliers of Northwind Traders through our Monorail application.

The structure of Northwind Traders project follows Monorail standards: we have a Monorail project, much like a traditional webforms project, and it has separate folders for Models, Views and Controllers.

The Models folder contains the entities Product and Supplier, which are persisted to the Sql Server database through the ActiveRecord framework.

The Views folder contains the .vm files, which are basically NVelocity template files used by Monorail to generate the final html code for the view.

The Controllers folder contains the controller classes, ProductController and SupplierController. Each controller has the methods representing the actions emitted against the controller to perform the CRUD functionalities on the entities.

Url routing

Unlike WebForms websites, where each url is redirected to a physical file in the website, in Monorail the url is written to be re-routed not to a file, but to a specific action in a specific controller, following this format:

http://website/MonorailApplication/controller/action.rails

Example:

http://localhost/monorail/product/masterdetail.rails

The result of this request is the rendering of the following page:

Let's try to understand how we got there from our url:

http://localhost/monorail[1]/product[2]/masterdetail[3].rails[4]

[1] monorail is our website.
[2] product tells Monorail framework to instantiate the ProductController class.
[3] masterdetail tells Monorail framework to invoke the MasterDetail method in the ProductController class.
[4] .rails is already configured in IIS as an extension associated with the ASP.Net ISAPI. Once ASP.Net is called, it investigates our web.config file, where there is a configuration (httphandlers tag) that tells ASP.Net to redirect every ".rails" request to the Monorail Framework.

The Domain Model

I could have added more entities to our model, but for the sake of simplicity, I decided to keep only Product and Supplier. Each entity class is inherited from ActiveRecordBase class, which automatically provides Refresh, Delete, Update, Create and Save functionalities.

The code below represents the Product class:

using System;
using Castle.ActiveRecord;

namespace Northwind_Monorail.Models
{
    [ActiveRecord("Products")]
    public class Product : ActiveRecordBase<Product>
	{
		private int id;
		private String name;
		private decimal price;
		private Supplier supplier;

		[PrimaryKey("ProductID")]
		public int Id
		{
			get { return id; }
			set { id = value; }
		}

		[Property("ProductName")]
		public string Name
		{
			get { return name; }
			set { name = value; }
		}

		[Property("UnitPrice")]
		public decimal Price
		{
			get { return price; }
			set { price = value; }
		}

		[BelongsTo("SupplierId")]
		public Supplier Supplier
		{
			get { return supplier; }
			set { supplier = value; }
		}
		
		public new static Product[] FindAll()
		{
			Product[] products = (Product[])FindAll(typeof(Product));
			return products;
		}

		public static Product FindById(int id)
		{
			return (Product) FindByPrimaryKey(typeof(Product), id);
		}
	}
}

Just a few notes on the Product class:

Note that the Product class is decorated by the [ActiveRecord("Products")] attribute, which means that the Product class is mapped to the Products table in Northwind database.

The Id property is decorated by [PrimaryKey("ProductID")], which means that it is mapped to Products's primary key column (ProductID) in Northwind database.

Each non-key property is mapped to the table through the [Property()] attribute.

The Product class has a reference to the Supplier class. This is done by the Supplier property, which is of Supplier type. The attribute [BelongsTo("SupplierId")] informs which property of the Suppliers (SupplierID) is the foreign key property.

The Views

The view files in our project have the .vm extension, which means they will be processed by NVelocity. NVelocity is a template engine, that is, NVelocity files will be injected with information from controllers in order to form the final HTML code. You can use other view engines, like brails or even .aspx (although this last one is not advisable, since you wouldn't be able to use Web Controls). But here we will deal with NVelocity view engine only.

As an example, the following code snippet represents the index.vm file:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
        "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
  <head>
    $AjaxHelper.GetJavascriptFunctions()
    $ScriptaculousHelper.GetJavascriptFunctions()

    <script language="javascript" type="text/javascript">
.
.
.
    <div id="headerwrap">
      <div id="header">
        #parse("menu\\headermenu.vm")
      </div>
      <div id="middlewrap">
        <div id="middle">
          <div id="sidebar">
            #parse("menu\\shortcut.vm")
          </div>
          <div id="content">
            <div id="statusbar"></div>
            <div id="details">#parse("product\\edit.vm")<div>
            <div id="search">#parse("product\\search.vm")</div>
            <div id="list">#parse("product\\list.vm")</div>
          </div>
        </div>
      </div>
    </div>
    <div id="footerwrap">
      <div id="footer">
      </div>
    </div>
  </body>
<html>

Notice the #parse directives in the view above. The role of the #parse directive is to render the content of another view within the view, so that you can keep clean, small and cohesive views for your website.

The following picture explains how partial views are rendered by the main product view (index view):

The Controllers

The code below represents the ProductController class:

using System;
using System.Collections;
using System.Collections.Generic;
using Castle.MonoRail.Framework;
using Castle.MonoRail.Framework.Helpers;
using Castle.Monorail.JSONSupport;
using Newtonsoft.Json;
using NHibernate.Expression;
using Northwind_Monorail.Models;
using Northwind_Monorail.Queries;

namespace Northwind_Monorail.Controllers
{
    [Layout("default"), Rescue("generalerror"), Helper(typeof(JSONHelper), "Json")]
	public class ProductController : SmartDispatcherController
	{
.
.
.
        public void Index([DataBind("product", Validate = true)] Product product)
        {
            PropertyBag["products"] = new Product();
            string productName = "";
            int supplierId = 0;
            PropertyBag["products"] = PaginationHelper.CreatePagination(this, GetProducts(productName, supplierId), 10);
            PropertyBag["suppliers"] = GetSuppliersWithABlankItem();

            List shortcuts = new List();
            Shortcut scProduct = new Shortcut();
            scProduct.Text = "Products";
            scProduct.Image = "\\Images\\products.gif";
            scProduct.Url = "\\product\\Index.rails";
            scProduct.DetailUrl = "\\product\\edit.rails";
            scProduct.SearchUrl = "\\product\\search.rails";
            scProduct.ListUrl = "\\product\\list.rails";
            scProduct.Tooltip = "Manage Products";
            Shortcut scSupplier = new Shortcut();
            scSupplier.Text = "Suppliers";
            scSupplier.Image = "\\Images\\suppliers.gif";
            scSupplier.Url = "\\supplier\\Index.rails";
            scSupplier.DetailUrl = "\\supplier\\edit.rails";
            scSupplier.SearchUrl = "\\supplier\\search.rails";
            scSupplier.ListUrl = "\\supplier\\list.rails";
            scSupplier.Tooltip = "Suppliers";

            shortcuts.Add(scProduct);
            shortcuts.Add(scSupplier);

            PropertyBag["shortcuts"] = shortcuts;
        }
.
.
.

Suppose you request the following url to the website:

http://localhost/monorail/product/index.rails

The following events will take place:

1. The Monorail framework will invoke the action (i.e. the index() method) of an instance of the ProductController class.
2. The index method will retrieve data from model (both product and supplier data) and store it in PropertyBag list.
3. After the execution of product controller, the Monorail framework will render the view corresponding to the action (index.vm).
4. The view will populate the dropdown list with supplier information, and the grid with product information.

Downloading and Installing the Sample Application

Installing Northwind Database

Since the sample application depends on the Northwind database:

You must have a local Sql Server 2000 or 2005, or have access to a remote one.

Make sure your server has a Northwind sample database installed. If not, please download it from Microsoft Download Center and restore it on your server.

IIS Configuration

A request to a Monorail application is identified by the IIS by the url extension. Usually, that extension is .rails (like in our sample), but you can use other extensions, if they aren't in use yet. When users you call a url of your Monorail web application, the Internet Information Server must first pass that information to the ASP.Net ISAPI, so that the Asp.Net framework can read your app's web.config, where there is an explicit instruction to hand over control to the Monorail framework whenever the .rails extension is found:

<httpHandlers>
	<add verb="*" path="*.rails"
	type="Castle.MonoRail.Framework.MonoRailHttpHandlerFactory,
	Castle.MonoRail.Framework"/>
.
.
.
</httpHandlers>

Httphandler tag in Web.config file

But in order to the .rails extension be processed, it must first be associated with the ASP.Net ISAPI. You can do it by configuring IIS as follows:

1. Open IIS Management Console
2. Right-click the Default Web Site item and choose Properties
3. Select the Home Directory tab
4. Click Configurations

5. Click Add
6. Select the ISAPI DLL. You can copy-and-paste the complete DLL file name from another extension, such as .aspx. In most systems it will be something like C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\aspnet_isapi.dll (for .NET 1.1) or C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll (for .NET 2.0).
7. Fill in the extension (for example .rails) as the file extension (make sure you do not omit the leading dot)
8. Uncheck the Check file exists check box

For more detailed information, see: Installing Monorail

Note: We had to perform this configuration above in the IIS because in this sample we are using the .rails extension. However, as our reader mentifex pointed out in his comments, you can make your life easier by changing your web.config file to use the .ashx extension instead of .rails. ASHX (ASP.NET Web Handler File) is a Asp.Net native extension, and you don't have to configure manually its mapping on the IIS, since it is already mapped to the ASP.Net ISAPI. Besides, in cases when you don't have permission to change your IIS configuration, .ashx is your only choice. Just change your web.config to map .ashx files to Monorail framework, and you're done.

Downloading the Sample Application

Next, you download the Northwind Traders application attached to this article to a local folder:

Then you create a virtual directory for the application:

Important: Make sure your site was created for ASP.NET 2.0.

That's it!

Downloading the Source Code

In order to open the Northwind Monorail project attached to this article, you should first install Castle Project Release Candidate 3 MSI.

History

2008-02-19: created.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Marcelo Ricardo de Oliveira

Member

Marcelo Ricardo de Oliveira is MCSD.NET/MCAD and is software developer at Spring Wireless Brasil (São Paulo - Brazil), a leading end-to-end mobile business solutions provider.

Occupation:	Software Developer
Company:	Spring Wireless
Location:	Brazil

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Default view and nested controller actions

Thomas Eyde

14:54 25 Feb '08

A Monorail controller uses the action name as the default view, right?

What happens when I have two actions, say Add and List, and then decide to let the Index action call the List action? Which view is the default, now?


public class ProductController
{
  public void Index()
  {
    List();
  }

  public void List()
  {
    // stuff data into property bag.
  }
}

My intention is to have List as my default action, as well.

2.00/5 (1 vote)

Re: Default view and nested controller actions

etal

22:51 25 Feb '08

Obviously There can only be one default, if you want the list to be the default action for this controller you can use a DefaultAction attribute on the controller:


[DefaultAction("List")]
public class ProductController
{
    ....
}

By doing what you have done, when the framework invokes the index action it will still use the index view. The list method will be called and executed just like any normal class method but that does not affect the inner workings of the framework.

Other options would be to use a redirect:


public class ProductController
{
    public void Index()
    {
        RedirectToAction("List");
    }
}

Or you can manually set the list view to render in the index action:


public class ProductController
{
    public void Index()
    {
        List();
        RenderView("List");
    }
}

It all depends on what you are looking to archive.

Re: Default view and nested controller actions

Thomas Eyde

0:29 26 Feb '08

Thanks. You confirmed what I thought.

RedirectToAction seems a little strange to me, when the action is just a method call away. However, that seems to be the proper thing to do in my scenario.

It's too late for Monorail, but I am starting to think the default view wasn't such a good idea after all. It's probably not that often we need to jump to another action, but when we do, we have to remember to either use RedirectToAction in the caller or RenderView in the callee. Both are easy to forget.

Re: Default view and nested controller actions

etal

1:46 26 Feb '08

You can choose to ignore the default and explicitly call `RenderView` in every action just like ASP.NET MVC does it. This way when using regular method calls the default will always be overridden and you won't have to use redirects inside a controller. Personally I've never seen anyone work this way, a default view per action is the way it is done on every other web framework out there.
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great

bdaniel7

13:28 25 Feb '08

I started today to play with Monorail in order to evaluate it for a project. so far I had only one problem: some content that was repeating. I extracted that content to a view but all day I could not find how to include it in another view. #parse("menu\\headermenu.vm") The "parse" method just solved my problem of reusing content. 2 thumbs up! Dan
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Re: great

Marcelo Ricardo de Oliveira

10:28 26 Feb '08

Thanks for replying, Dan. I'm glad it was useful for you. best regards, Marcelo
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nice to see monorail and a suggestion

mentifex

3:10 19 Feb '08

Nice article. Easy introduction. But you should write that its easier to just change ".rails" to ".ashx" in web.config.
Sign In·View Thread·PermaLink	4.20/5 (2 votes)

Re: nice to see monorail and a suggestion

Marcelo Ricardo de Oliveira

6:26 19 Feb '08

Hi mentifex! Suggestion taken (see the article again). Thanks a lot! Best regards, Marcelo
Sign In·View Thread·PermaLink	4.20/5 (2 votes)

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