Creating a Controller (VB)

The goal of this tutorial is to explain how you can create new ASP.NET MVC controllers. You learn how to create controllers both by using the Visual Studio Add Controller menu option and by creating a class file by hand.

Using the Add Controller Menu Option

The easiest way to create a new controller is to right-click the Controllers folder in the Visual Studio Solution Explorer window and select the Add, Controller menu option (see Figure 1). Selecting this menu option opens the Add Controller dialog (see Figure 2).

Figure 01: Adding a new controller(Click to view full-size image)

Figure 02: The Add Controller dialog (Click to view full-size image)

Notice that the first part of the controller name is highlighted in the Add Controller dialog. Every controller name must end with the suffix Controller. For example, you can create a controller named ProductController but not a controller named Product.

Listing 1 – Controllers\ProductController.vb

Public Class ProductController
    Inherits System.Web.Mvc.Controller

    '
    ' GET: /Product/

    Function Index() As ActionResult
        Return View()
    End Function

End Class

You should always create controllers in the Controllers folder. Otherwise, you’ll be violating the conventions of ASP.NET MVC and other developers will have a more difficult time understanding your application.

Scaffolding Action Methods

When you create a controller, you have the option to generate Create, Update, and Details action methods automatically (see Figure 3). If you select this option then the controller class in Listing 2 is generated.

Figure 03: Creating action methods automatically (Click to view full-size image)

Listing 2 – Controllers\CustomerController.vb

Public Class CustomerController
    Inherits System.Web.Mvc.Controller

    '
    ' GET: /Customer/

    Function Index() As ActionResult
        Return View()
    End Function

    '
    ' GET: /Customer/Details/5

    Function Details(ByVal id As Integer) As ActionResult
        Return View()
    End Function

    '
    ' GET: /Customer/Create

    Function Create() As ActionResult
        Return View()
    End Function

    '
    ' POST: /Customer/Create

    <AcceptVerbs(HttpVerbs.Post)> _
    Function Create(ByVal collection As FormCollection) As ActionResult
        Try
            ' TODO: Add insert logic here
            Return RedirectToAction("Index")
        Catch
            Return View()
        End Try
    End Function

    '
    ' GET: /Customer/Edit/5

    Function Edit(ByVal id As Integer) As ActionResult
        Return View()
    End Function

    '
    ' POST: /Customer/Edit/5

    <AcceptVerbs(HttpVerbs.Post)> _
    Function Edit(ByVal id As Integer, ByVal collection As FormCollection) As ActionResult
        Try
            ' TODO: Add update logic here

            Return RedirectToAction("Index")
        Catch
            Return View()
        End Try
    End Function
End Class

These generated methods are stub methods. You must add the actual logic for creating, updating, and showing details for a customer yourself. But, the stub methods provide you with a nice starting point.

Creating a Controller Class

The ASP.NET MVC controller is just a class. If you prefer, you can ignore the convenient Visual Studio controller scaffolding and create a controller class by hand. Follow these steps:

1. Right-click the Controllers folder and select the menu option Add, New Item and select the Class template (see Figure 4).
2. Name the new class PersonController.vb and click the Add button.
3. Modify the resulting class file so that the class inherits from the base System.Web.Mvc.Controller class (see Listing 3).

Figure 04: Creating a new class(Click to view full-size image)

Listing 3 – Controllers\PersonController.vb

Public Class PersonController
    inherits Controller

    Function Index AS String
        Return "Hello World!"
    End Function

End Class

The controller in Listing 3 exposes one action named Index() that returns the string "Hello World!". You can invoke this controller action by running your application and requesting a URL like the following:

http://localhost:40071/Person