MVC Controller

MVC controllers are responsible for handling incoming HTTP requests, handling user input, retrieving and saving data, and determining the response to send back to the client.

Each browser request is mapped to a particular controller.

Controllers are derived from System.Web.Mvc.Controller (built-in controller base class).

Action

Each public method on a controller class is an action method, which means you can invoke it from the web via some URL.

A method used as a controller action cannot be overloaded.

The method must be public.

The method cannot be a static or extension method.

The method cannot be a constructor, getter, or setter.

The method cannot have open generic types.

The method is not a method of the controller base class.

The method cannot contain ref or out parameters.

A controller action can be invoked by anyone connected to the Internet.

If you don’t want to expose the method as a controller action then you can prevent the method from being invoked by using the [NonAction] attribute.

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 several types of action results including:

Action Result	Description	Controller base class method
ViewResult	Represents HTML and markup	View
EmptyResult	Represents no result
RedirectResult	Represents a redirection to a new URL	Redirect
JsonResult	Represents a JavaScript Object Notation result that can be used in an AJAX application	Json
JavaScriptResult	Represents a JavaScript script	JavaScriptResult
ContentResult	Represents a text result	Content
FileContentResult	Represents a downloadable file (with the binary content)	File
FilePathResult	Represents a downloadable file (with a path)	File
FileStreamResult	Represents a downloadable file (with a file stream)	File