(MicroSoft.net MVC)

Small Introduction Of Model View Controller

Model

The Model component corresponds to all the data-related logic that the user works with. This can represent either the data that is being transferred between the View and Controller components or any other business logic-related data. For example, a Customer object will retrieve the customer information from the database, manipulate it and update it data back to the database or use it to render data.

View

The View component is used for all the UI logic of the application. For example, the Customer view will include all the UI components such as text boxes, dropdowns, etc. that the final user interacts with.

Controller

Controllers act as an interface between Model and View components to process all the business logic and incoming requests, manipulate data using the Model component and interact with the Views to render the final output. For example, the Customer controller will handle all the interactions and inputs from the Customer View and update the database using the Customer Model. The same controller will be used to view the Customer data.

ASP.NET MVC Routing enables the use of URLs that are descriptive of the user actions and are more easily understood by the users. At the same time, Routing can be used to hide data which is not intended to be shown to the final user.

For example, in an application that does not use routing, the user would be shown the URL as https://myapplication/Users.aspx?id=1 which would correspond to the file Users.aspx inside myapplication path and sending ID as 1, Generally, we would not like to show such file names to our final user.

To handle MVC URLs, ASP.NET platform uses the routing system, which lets you create any pattern of URLs you desire, and express them in a clear and concise manner. Each route in MVC contains a specific URL pattern. This URL pattern is compared to the incoming request URL and if the URL matches this pattern, it is used by the routing engine to further process the request.

MVC Routing URL Format

To understand the MVC routing, consider the following URL ?

http://servername/Products/Phones

In the above URL, Products is the first segment and Phone is the second segment which can be expressed in the following format ?

{controller}/{action} 

The MVC framework automatically considers the first segment as the Controller name and the second segment as one of the actions inside that Controller.

Note ? If the name of your Controller is ProductsController, you would only mention Products in the routing URL. The MVC framework automatically understands the Controller suffix.

Create a Simple Route

Routes are defined in the RouteConfig.cs file which is present under the App_Start project folder.

You will see the following code inside this file ?

public class RouteConfig { 
   
   public static void RegisterRoutes(RouteCollection routes) { 
      routes.IgnoreRoute("{resource}.axd/{*pathInfo}");  
      
      routes.MapRoute( 
         name: "Default", 
         url: "{controller}/{action}/{id}", 
         defaults: new { controller = "Home", action = "Index", 
            id = UrlParameter.Optional } 
      ); 
   } 
} 

This RegisterRoutes method is called by the Global.ascx when the application is started. The Application_Start method under Global.ascx calls this MapRoute function which sets the default Controller and its action (method inside the Controller class).

To modify the above default mapping as per our example, change the following line of code ?

defaults: new { controller = "Products", action = "Phones", id = UrlParameter.Optional } 

This setting will pick the ProductsController and call the Phone method inside that. Similarly, if you have another method such as Electronics inside ProductsController, the URL for it would be ?

https://servername/Products/Electronics

Types of Filters

ASP.NET MVC framework supports the following action filters ?

• Action Filters ? Action filters are used to implement logic that gets executed before and after a controller action executes. We will look at Action Filters in detail in this chapter.
• Authorization Filters ? Authorization filters are used to implement authentication and authorization for controller actions.
• Result Filters ? Result filters contain logic that is executed before and after a view result is executed. For example, you might want to modify a view result right before the view is rendered to the browser.
• Exception Filters ? Exception filters are the last type of filter to run. You can use an exception filter to handle errors raised by either your controller actions or controller action results. You also can use exception filters to log errors.

Action filters are one of the most commonly used filters to perform additional data processing, or manipulating the return values or cancelling the execution of action or modifying the view structure at run time.