Creating an Action (VB)
by Microsoft
Learn how to add a new action to an ASP.NET MVC controller. Learn about the requirements for a method to be an action.
The goal of this tutorial is to explain how you can create a new controller action. You learn about the requirements of an action method. You also learn how to prevent a method from being exposed as an action.
Adding an Action to a Controller
You add a new action to a controller by adding a new method to the controller. For example, the controller in Listing 1 contains an action named Index() and an action named SayHello(). Both methods are exposed as actions.
Listing 1 - Controllers.vb
[!code-vbMain]
1: <HandleError()> _
2: Public Class HomeController
3: Inherits System.Web.Mvc.Controller
4:
5: Function Index() As ActionResult
6: Return View()
7: End Function
8:
9: Function SayHello() As String
10: Return "Hello!"
11: End Function
12: End Class
In order to be exposed to the universe as an action, a method must meet certain requirements:
- The method must be public.
- The method cannot be a static method.
- The method cannot be an extension method.
- The method cannot be a constructor, getter, or setter.
- The method cannot have open generic types.
- The method is not a method of the controller base class.
- The method cannot contain ref or out parameters.
Notice that there are no restrictions on the return type of a controller action. A controller action can return a string, a DateTime, an instance of the Random class, or void. The ASP.NET MVC framework will convert any return type that is not an action result into a string and render the string to the browser.
When you add any method that does not violate these requirements to a controller, the method is exposed as a controller action. Be careful here. A controller action can be invoked by anyone connected to the Internet. Do not, for example, create a DeleteMyWebsite() controller action.
Preventing a Public Method from Being Invoked
If you need to create a public method in a controller class and you don’t want to expose the method as a controller action then you can prevent the method from being invoked by using the <NonAction> attribute. For example, the controller in Listing 2 contains a public method named CompanySecrets() that is decorated with the <NonAction> attribute.
Listing 2 - Controllers.vb
[!code-vbMain]
1: Public Class WorkController
2: Inherits System.Web.Mvc.Controller
3:
4: _
5: Function CompanySecrets() As String
6: Return "This information is secret."
7: End Function
8:
9: End Class
If you attempt to invoke the CompanySecrets() controller action by typing /Work/CompanySecrets into the address bar of your browser then you’ll get the error message in Figure 1.
Figure 01: Invoking a NonAction method(Click to view full-size image)
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