Overview of the Chapter

This chapter starts by discussing introductory topics you need to understand to write custom controls. It then provides the steps to create the application in the section "Implementing the Project".

More specifically, the following are the main sections in this chapter:

"Using the Control and UserControl Classes": This section describes the two members of the System.Windows.Forms namespace that you extend when writing a custom control. This section provides you with a general description of the two controls.

"Drawing the Graphical User Interface": This section explains how to draw the GUI part of a custom control. You will develop the RoundButton control, a simple button with a circular shape.

"Capturing Key Presses": This section looks at the different types of keys on a computer keyboard and discusses what happens when the user presses a key. It then explains how to capture a user key press and how your application can respond to a key press.

"Creating Events with Delegates and the Observer Design Pattern": This section explains how events work, discusses the Observer design pattern, and illustrates how to write a custom event in step-by-step instructions.

"Understanding the Model-View-Controller (MVC) Paradigm": This section explains the MVC paradigm used in many GUI controls. The StyledTextArea control is based on this model; therefore, understanding MVC is crucial.

"Implementing the Project" This section thoroughly explains the StyledTextArea control. It starts from the specification and the class diagram and then continues with a detailed discussion of each class and its members. At the end of this section, the "Using the StyledTextArea Control" subsection presents an application that uses this custom control.