.NET Windows Forms in a Nutshell

Chapter 2. Controls

The System.Windows.Forms namespace defines a class called Control. This class is at the heart of all Windows Forms applications. Any visual element of an application—whether it is a window, a button, a toolbar, or a custom user-defined control—is represented by an object of some class deriving from Control.

This chapter describes the role played by the Control class within the Windows Forms framework, and examines the basic behavior that all controls inherit from Control. It also introduces the classes that represent the traditional Windows controls.

Windows Forms and the Control Class

Each different type of user interface element is represented by a specialized class deriving from Control. For example, top-level windows are represented by the Form class; each of the standard Windows control types has a corresponding class (such as Button and TreeView); you can also define custom controls by creating your own classes. All these inherit (either directly or indirectly) from the Control class.

Because all visual elements derive from Control, they share a single implementation of the features common to all controls. This ensures a certain minimum level of functionality and guarantees consistent behavior across all control types. The Control class defines standard properties, events, and methods for all the common features of user interface components. These include size and position, input handling, and appearance.

The Control class also defines the nature of the relationships ...