Understanding Controller In ASP.NET MVC

Overview

In the earlier article, we saw how to create a sample Application in MVC in version 4.0 and 3.5. We saw about Controller class and its various action methods.

• Introduction To ASP.NET MVC

Here, in this article, we will see more about the controllers and understanding about RouteConfig File. I will be using the same solution which we had used in our previous article. Thus, let's start an introduction.

• Open our solution MVCTestApplication, given below:
  
  
  

You can see in our Home Controller class; we have two Action methods; one is Index() and other is HelloAll() . The Index methods are invoked, when you run the Application. Now, just run the Application and you will see:


By default, Hello CsharpCorner has been displayed, because in RouteConfig file, the default action method is Index and we had written “Hello CsharpCorner ” in Index Action Method.

Now, let's type the URL i.e. ControllerName/ActionName and see what we are getting: 


As you can see, we had got the same result: “Hello CsharpCorner.” Here, Home is our ControllerName and Index is our Action Method . Similarly, we will see our second Action Method i.e. HelloAll()


As you can see, HelloAll() Action Method has been invoked .

Now, let's understand RouteConfig and how these controllers are displayed .

Just Open global.asax file in our solution and you will see:




Open this file and you will see Application_start () method, in which you will see this line as:


Go to its Definition section, it will redirect to RouteConfig File and you will see:





In RouteConfig class, we have default document as:

name:”Default”-Specifies the name

URL: “{Controller}/{action}/{id}” – This line actually says that when you run the solution by default, it will first fire the controllername/index and then Id.

Defaults: As you can see, the default controller' s Home is called and is followed by the action Index and then Id.

Note: Here the specified Id is normal and if you want to retrieve the results, you have to pass the Id .

• Now, we will see how to pass the Id in our URL and see what output we are getting. Hence, let's start:
  
  
  
  In our Homecontroller class, in our Index Action method, just pass a parameter as a string name and return as a name . Now, we will run the Application and see what values we are getting.
  
  
  When you run the solution, it will ask for the name. Now, let's pass the name in our URL:
  
  
  As you can see in the output, given above, it had passed Id=1 and got Id=1.
  
  Just type Home/index/1 an you will get the output, given above.
  
  Now, we will modify the code, write the name and see the output that we will get:
  
  
  
  I had passed the name. Now, run the Application. You will see the following output:
  
  
  Now, just pass the Id and name.
  
  
• We saw the last Id, how to specify the Id or name and how to display it. Now, let's get back to the RouteConfig file and understand the line, given below:
  
  
  

Here, what this line says is: Whatever you are doing in the Controller or in the Index Action method, a trace is getting generated in the form of axd format. We will see how these are generated and how to generate a resource.axd trace. Just open web.config file, shown below:



Just write this line in your web.config file.



Now, run the Application and type trace.axd. You will see the following output:



Click the View details and you will get all the details, shown below: 



Scroll down at the bottom of the page and you will see that its path, query string and its respective URLs are:



The trace.axd is useful, when you have built a huge application and you require tracing to find out the details.

Conclusion: This was controllers in MVC. I hope you found this article helpful.