Visual Basic® 2010 Unleashed

Contra Variance

Contra variance basically works the opposite of covariance: From a derived class we can take advantage of an abstract class or of a base class. To understand how contra variance works, the best example is to create a client application in which two events of the same control are handled by the same event handler. For this, create a new Windows Presentation Foundation application and write the following XAML code to define a simple Button control:

<Button Content="Button" Height="50" Name="Button1" Width="150" />

Creating WPF Applications

If you are not familiar with WPF applications, you notice one important thing when creating such projects: The designer provides a graphical editor and the code editor for the XAML code (which ...