Introduction to ASP.NET MVC 3

Introduction

ASP.NET MVC framework follows the well-defined MVC pattern to create a web application. MVC design pattern is used to separate the different parts of the application for more scalability, extensibility and testability purposes.
One of the major challenges with normal web forms is the testability of the business logic. Unit test of code-behind logic is very complex. Also, the extensibility of the application required a lot of re-work on the application. ASP.NET MVC addresses the pain points associated with the traditional web form applications.
In this article, we will discuss about how to create an MVC application and understand the Controller, Views & Models.

MVC

MVC means Model View Controller. Controller takes care of the overall execution of a request. Controller receives the request from the web server and identifies the data requirements. Depending on the data requirements, Controller contacts the corresponding Model. Model will supply the required data, which will be rendered to the UI using a View.
For working with ASP.NET MVC, we can install the Web Platform Installer, which consists of Visual Studio 2010 Express for coding the MVC application, SQL Server Express for storing the data and IIS Express for hosting the application. We can download the Web Platform Installer from Microsoft Web Platform Installer 3.0.

How to Create an ASP.NET MVC Application

Let us start our discussion by creating the first MVC application. File-> New Project and select the ASP.NET MVC 3 Web Application template.
This will open the new ASP.NET MVC 3 Project window.
Select either Empty or Internet Application. Empty will create a blank application. Internet application will create an application with few default pages. For our sample, I will select the Internet Application option.
We can choose to create a test project along with our MVC application from the same window. Also, we can choose the View Engine as ASPX or Razor. ASPX is for backward compatibility.
Our new solution will look like:
We have different folders to hold the Controllers, Views and Models. As we selected Internet Application, our application is a fully functional application. We can run it and see the pages.
It opens a small application with two tabs, Home and about. Also, we have the option to Log On, from where we can register a new User.
When you select the About tab, it goes to the HomeController and returns a View using the About() method. About() is not specified any View name, so the controller will goes to the Views and find the directory corresponding to the HomeController. Here also, it uses the name of the controller to find the corresponding directory. Then, the controller checks whether it contains any view with the name About.
We can specify a View name in the About() method like:

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public ActionResult About()
{
    return View("Index");
}

Now, both Home and About display the same content.

Data Passing from Controller to View

Now, let us see how we can pass some information to the View from Controller. There are two ways to pass data from Controller to View.

Using ViewBag

ViewBag is a dynamic object, where we can add any properties dynamically.
For example, if I want to pass some contact information like Name and Contact number to About View from the Home controller, we can define it using the ViewBag as:

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public ActionResult About()
{
    ViewBag.ContactPerson = "George MAthew";
    ViewBag.ContactNumber = "91-99444444000";
    return View();
}

This data will be accessed in about.cshtml as:

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@{    
   ViewBag.Title = "About Us";
}
<h2>About</h2>
<div>    
      Contact person : @ViewBag.ContactPerson 
      Contact Number : @ViewBag.Contactnumber
</div>

Note that the dynamic properties added are not case sensitive. Also, it won’t throw any exception, in case of a wrong dynamic property reference.
Now, our About tab looks like:

Using Model

Now, let us see how we can pass data using a Model. Define a Model class and specify the required properties. Our sample Model class looks like:

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namespace SampleApp.Models
{
    public class ContactAddress   
    {
       public string Address { get; set; }
       public string City { get; <br />set; }
       public string Country { get; set; }
    }
}

Now, let us construct the Model in Controller and pass the same to our View:

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public ActionResult About()
{
    var address = new ContactAddress()
    {
        Address = "Lane 21, Gachibowli",
        City = "Hyderabad",
        Country = "India"
    };
    
    return View(address);
}

Now, we will use the same in our View. In View, we have another object called Model, which holds the dynamic properties like ViewBag. We can extract the model properties using Model.

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@{
    ViewBag.Title = "About Us";
}
<h2>About</h2>
<div>
  Contact Address: @Model.Address, @Model.City, @Model.Country
</div>

Now, our About tab looks like:
Notice that there is no intellisense support for the Model properties. We can define the type of the expected model on top of the View, which will gives the Intellisense support for the Model object.

Conclusion

In this article, we discussed about the ASP.NET MVC framework, how to create a basic MVC application and discussed about the Controller to View communication. We have a lot more to discuss in MVC like the Content folder holding all images and styles, Scripts folder with jQuery scripts and MVC detail. We will discuss the topics in detail later.