Microsoft® Visual Studio® 2010 Unleashed

Subclassing an Existing Control

Subclassing an existing control is the best approach if your needs are only slightly different from one of the standard .NET Framework controls. By inheriting from an existing control class, you are riding on top of its behavior and appearance; it’s up to you to then add the specialized code to your new control class.

For example, suppose that you want a text box that turns red anytime a numeric (that is, nonalphabetic) character is entered. This is easy to do with just a few lines of code sitting in the TextBox control’s TextChanged event, but consolidating this behavior into its own class provides a reuse factor.

You start by adding a new user control to the project. User controls actually inherit from the UserControl ...