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ASP.Net MVC –Understanding Controllers

Controllers


 
MVC controllers are responsible for responding to requests made against an ASP.NET MVC website. Each browser request is mapped to a particular controller.

 
A controller is a class that derives from the base System.Web.Mvc.Controller class. Because a controller inherits from this base class, a controller inherits several useful methods .The following doe depicts a controller

 
  
Figure-1


 
Understanding Controller Actions

 
A controller exposes controller actions. An action is a method on a controller that gets called when a particular URL is entered in the browser address bar.

 
For e.g. consider the following URL

 
http://localhost/TestController/Index/3

 
In the above example, Index () method is called on the TestController class. The Index () method is an example of a controller action.

 
Following are the considerations that need to be made while writing controller actions.

 
• A controller action must be a public method of a controller class. Any public method added to a controller class is exposed as a controller action automatically.


• A method used as a controller action cannot be overloaded.


• A controller action cannot be a static method.

 
Understanding Action Results

 
A controller action returns something called an action result. An action result is what a controller action returns in response to a browser request.

 
The ASP.NET MVC framework supports following types of action results:

 
  • ViewResult: Represents HTML and markup. 
  • EmptyResult: Represents no result. 
  • RedirectResult: Represents a redirection to a new URL.
  • JsonResult: Represents a JavaScript Object Notation result that can be used in an AJAX application.
  • JavaScriptResult: Represents a JavaScript script.
  • ContentResult: Represents a text result.
  • FileContentResult: Represents a downloadable file (with the binary content).
  • FilePathResult: Represents a downloadable file (with a path).
  • FileStreamResult: Represents a downloadable file (with a file stream).
 All of these action results inherit from the base ActionResult class.

 
Index () action in Figure-1 does not return a ViewResult (). Instead, the View () method of the Controller base class is called. Normally, an action result is not returned directly. Instead, one of the following methods of the Controller base class is called:

 
  • View - Returns a ViewResult action result.
  • Redirect - Returns a RedirectResult action result.
  • RedirectToAction - Returns a RedirectToRouteResult action result.
  • RedirectToRoute - Returns a RedirectToRouteResult action result.
  • Json - Returns a JsonResult action result.
  • JavaScriptResult - Returns a JavaScriptResult.
  • Content - Returns a ContentResult action result.
  • File - Returns a FileContentResult, FilePathResult, or FileStreamResult depending on the parameters passed to the method.
 
 
  Figure-2


 
In Figure-2, depending upon whether the id is null, either a redirection to index action is made or a View is returned.

Figure-3


If a controller action returns a result that is not an action result - for example, a date or an integer - then the result is wrapped in a ContentResult automatically, else the ContentResult needs to be exclusively used in the code as depicted in Figure-3.


Hope the details provided here are helpful.

Till next we connect…..



Happy Learning.



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