Adding a Controller in ASP.NET MVC 5 Application

First We Describe  What is MVC ?

1. MVC stands for model-view-controller.  MVC is a pattern for developing applications that are well architected, testable  and easy to maintain. MVC-based applications contain:
   • Models: Classes that represent the data of the application  and that use validation logic to enforce business rules for that data.
   • Views: Template files that your application uses to dynamically  generate HTML responses.
   • Controllers: Classes that handle incoming browser requests,  retrieve model data, and then specify view templates that return a response  to the browser.
   
   Let's Adding a Controller in ASP.NET MVC 5 Application.
   
   1 .When you create new ASP.NET MVC 5 Project. By Default Project is created in Visual studio .
   
   2  In Solution  Explorer, right-click the Controllers folder  and then click Add,  then Controller.
   
   
   
   
   3 In the Add Scaffold dialog box, click MVC 5  Controller - Empty, and then click Add.
   
   
   
   
   4 Name your new controller "HelloWorldController" and click Add.
   
   
   
   
   5 Notice in Solution  Explorer that a new file  has been created named HelloWorldController.cs and a new folder Views\HelloWorld. The controller is open in the IDE.
   
   
   
   
   6 Replace the contents of the file with the following code.
   

   using System.Web;
   using System.Web.Mvc; 
    
   namespace MvcMovie.Controllers 
   { 
       public class HelloWorldController : Controller 
       { 
           // 
           // GET: /HelloWorld/ 
    
           public string Index() 
           { 
               return "This is my default action..."; 
           } 
    
           // 
           // GET: /HelloWorld/Welcome/ 
    
           public string Welcome() 
           { 
               return "This is the Welcome action method..."; 
           } 
       } 
   }

      The controller methods will return a string of HTML as an example. The controller is named HelloWorldController and  the first method is named Index.  Let’s invoke it from a browser. Run the application (press F5 or Ctrl+F5). In the  browser, append "HelloWorld" to the path in the address bar. (For example,  in the illustration below, it's http://localhost:1234/HelloWorld.)  The page in the browser will look like the following screenshot. In the method above, the code returned a string directly. You told the system to just return some HTML, and it did! 
   
   
   
   
   
   
   NOTE :
   
   
    ASP.NET MVC invokes different controller classes (and different action methods within  them) depending on the incoming URL. The default URL routing logic used by ASP.NET  MVC uses a format like this to determine what code to invoke:
   /[Controller]/[ActionName]/[Parameters]

      

You set the format for routing in the App_Start/RouteConfig.cs  file.

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 }
    );
}

 
When you run the application and don't supply any URL segments, it defaults to  the "Home" controller and the "Index" action method specified in the defaults  section of the code above.


The first part of the URL determines the controller class to execute. So /HelloWorld maps  to the HelloWorldController class.  The second part of the URL determines the action method on the class to execute.  So /HelloWorld/Index would  cause the Index method of the HelloWorldController class to execute. Notice that we only had to browse to /HelloWorld and  the Index method  was used by default. This is because a method named Index is the default method that will be called on a controller if one is not explicitly specified. The third part of the URL segment ( Parameters) is for route data. We'll see route data later on in this  tutorial.



MORE Interesting Example.

 Let's Modify Welcome method as below.

public string Welcome(string name, int numTimes = 1) {
     return HttpUtility.HtmlEncode("Hello " + name + ", NumTimes is: " + numTimes);
}

In ASP.NET MVC applications, it's more typical to pass in parameters as route  data than passing them as query strings. You could also  add a route to pass both the name and numtimes in  parameters as route data in the URL. In the App_Start\RouteConfig.cs  file, add the "Hello" route:

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 }
      );

      routes.MapRoute(
           name: "Hello",
           url: "{controller}/{action}/{name}/{id}"
       );
   }
}

Now  Run the application and browse to /localhost:XXX/HelloWorld/Welcome/Scott/3.