In addition to creating user controls, which are essentially reusable small web pages, you can also create your own compiled custom controls. There are three ways to create custom controls:
Create a derived custom control by deriving from an existing control.
Create a composite control by grouping existing controls together into a new compiled control.
Create a full custom control by deriving from System.Web.UI.WebControls.WebControl.
Composite controls are most similar to user controls. The key difference is that composite controls are compiled into a DLL and used as you would any server control.
To get started, you’ll create a Web Control Library in which you’ll create the various custom controls for this chapter. Open Visual Studio .NET and choose New Project. In the New Project Window, select either Visual C# Projects or Visual Basic Projects and create a Web Control Library called CustomControls, as shown in Figure 14-7.
Figure 14-7. Custom control New Project window
You’ll notice that Visual Studio has created a complete custom control named WebCustomControl1. Before examining this control, create a Web Application to test it. From the File menu choose New Project (Ctrl-Shift-N) and create a project named CustomControlWebPage in the same directory. Be sure to choose the “Add to Solution” radio button, as shown in Figure 14-8.
Figure 14-8. Add custom control web page ...