Technology Tutorials: MVC Tutorial Part 3 : Create Controller

In this demo we will be learning :

1. How to create a controller

2. Displaying text on screen

3. Overview of URL redirecting in MVC for Contoller

Lets start by launching VS for web, we will name this project as Demo2.

we will be making use of “Internet Application” and “ASPX” as our view engine.

This will create Demo2 project as below:

Now, we will be adding a new Controller. For this, right click on Controller folder in Solution Explorer and navigate to Add >> Controller and click on Controller this will open Add Controller window.

Rename this Contoller as EmployeeController.

Note : All controller should be ending with name Controller. To know why read :

http://stackoverflow.com/questions/759617/naming-conventions-one-rule-for-controllers-no-rules-for-models-and-views

Do not select any Template, we will learn how to make use of templates later. Just click Add. This will add a new Controller inside Controller folder with name EmployeeController.cs also VS will open the file up for you.

Explanation of controller code :

Public ActionResult Index()

{

}

This is a declaration of method named Index(), which is declared inside a Controller, more than one method can be declared inside a controller and any method which is declared inside a controller can also be called action method.

Now, delete the ActionRestult method in code and add below String method to the code.

public string HrDepartment()

{

return "Employee in HR Department is Called";

}

public string PayrollDepartment()

{

return "Employee in Payroll Department is Called";

}

Page will look as below :

Explanation of Code :

public string HrDepartment()

{

return "Employee in HR Department is Called";

}

Here HrDepartment() is our ActionMethod in Controller Employee & it will return a string.

Now lets run the application, you will get default application screen. Now to access and get values from the controller we need to change the URL in address bar of the browser.

Let’s change it to :

http://localhost:*****/Employee/HrDepartment

Syntax => http://localhost:*****/ControllerName/ActionName

So, now to print the next set of output change URL to http://localhost:*****/Employee/PayrollDepartment

So, we are now able to display values on screen without using View. Controller can be used to display text sentences on the screen. But, to make a fullfledge web page design you require View.

Now lets understand how URL concept work. (URL redirections plays a major part in MVC, There will be detailed chapter later on URL concept and its working)

To understand this better now lets run our application and redirect to http://localhost:*****/Employee this will give an Error page. This is because we don’t have an Index() method declared in our Controller. Index method works as a default method for a controller, and even when we don’t make use of action name in URL it redirects to Index method if its declared in our controller.

Declare a Action Method Index() in our Employee Controller.

public string Index()

{

return "Index Method is called, Index method works as an Default action for a controller";

}

Your Employee controller will look as below:

Run the project and redirect to http://localhost:*****/Employee again. This time MVC will rediect to Index actionmethod inside Employee Controller. Which shows Index works as an default actionmethod for an Controller.

So now if you look at Home page URL its states only localhost:*****, lets know how and where is this setup.

This page is coming from Home Controller and Index Action. Even if you extend your URL to localhost:*****/Home/Index, it will take you to the same page.

So, how is MVC handling this short URL, this is called URL Rewriting. URL rewriting hides page name and other details from end user.

In MVC 4.0 it is done making use of Global.ascx.cs and RouteConfig.cs files. In Solution Explorer you will find Global.ascx file, it has its code behind file called Global.ascx.cs, when you open this file you will find below lines in Application_Start() method. (Application start method is the method which is called when application load)

Line No: 23

RouteConfig.RegisterRoutes(RouteTable.Routes);

Right Click on RegisterRoute and navigate to “Go to Definition”, it will take us to RouteConfig.cs which is located inside folder App_Start, this is where our URL rewriting is done.

Now let’s understand the code in RouteConfig.cs

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 }

);

}

Line No 14:

routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

Above line will not allow user to get any file ending with .axd in your Solution. As the name suggests IgnoreRoute suggests that no one should be able to access any file with extension .axd, in the same way we can hide other files like .pdf, .jpg, etc.

routes.MapRoute(

name: "Default",

url: "{controller}/{action}/{id}",

defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }

);

Whenever a call is made by browser, a call is made to MapRoute to check what redirects are in place.

Here, url: "{controller}/{action}/{id}", defines the sequence of invocation of the URL. I.e. in the URL Controller should be called first, then action later to it id.

defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional },

This defines which default file to call and which action to invoke. Here id is optional, because of which even when we are not passing it in URL its working fine and taking us to Home/Index.

We will be learning creation of Views in next chapter