Controllers in MVC application

In this article we will discuss about controllers. In previous article , we discussed that, the URL - http://localhost/MVCDemo/Home/Index will invoke Index() function of HomeControllerclass. So, the question is, where is this mapping defined. The mapping is defined in Global.asax. Notice that in Global.asax we have RegisterRoutes() method. 
RouteConfig.RegisterRoutes(RouteTable.Routes); 


Right click on this method, and select "Go to Definition". Notice the implementation of RegisterRoutes() method in RouteConfig class. This method has got a default route.
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 }
    );
}

The following URL does not have id. This is not a problem because id is optional in the default route.
http://localhost/MVCDemo/Home/Index

Now pass id in the URL as shown below and press enter. Nothing happens.
http://localhost/MVCDemo/Home/Index/10

Change the Index() function in HomeController as shown below.
public string Index(string id)
{
    return "The value of Id = " + id;
}

Enter the following URL and press enter. We get the output as expected.
http://localhost/MVCDemo/Home/Index/10

In the following URL, 10 is the value for id parameter and we also have a query string"name".
http://localhost/MVCDemo/home/index/10?name=Pragim

Change the Index() function in HomeController as shown below, to read both the parameter values.
public string Index(string id, string name)
{
    return "The value of Id = " + id + " and Name = " + name;
}

Just like web forms, you can also use "Request.QueryString"
public string Index(string id)
{
    return "The value of Id = " + id + " and Name = " + Request.QueryString["name"];
}