将方法添加到VB.Net中的.Net类库的类？

Question

I would like to know whether exists a way to add a method inside a class of the .Net framework class library.

Let's say for example that I would like to create a Class/module that adds an IsEmpty function in the System.Windows.Forms.Clipboard Class, is this possibly?, if not, Maybe I can do it in one of the My namespace? ( My.Computer.clipboard )

What alternatives I have instead wrapping the entire class? (and that should be done manualy? that's insane)

Answer 1

You are looking for extension methods: http://msdn.microsoft.com/en-us/library/bb384936.aspx

An extension method can be only a Sub procedure or a Function procedure. All extension methods must be marked with the extension attribute <Extension()> . The first parameter in an extension method definition specifies which data type the method extends.

Below is a brief example. (Fair warning, I am a C# developer, but I think this is the correct VB syntax.)

Imports System.Runtime.CompilerServices

Module MyExtensions

    <Extension()> 
    Public Sub MyFunction(ByVal obj As TypeToAddFunctionalityTo)
        ' functionality here
    End Sub 

End Module

Note that for the System.Windows.Forms.Clipboard class in particular, extension methods won't be of any help. Extension methods allow functions to be added to instance types. In the case of a class that is used statically, such as Clipboard , you won't ever have any instances of it.

Additionally, you cannot inherit from the Clipboard class because it is defined as NotInheritable . Creating a wrapper class is possible, however, I would recommend simply creating a static MyClipboardUtils class that works as an addendum/sibling to the built-in class.