Programming ASP.NET 3.5, 4th Edition

Custom Controls

In addition to creating user controls, which are essentially reusable portions of web pages, you can create your own compiled custom controls. As noted earlier, there are three ways to create custom controls: derive a control from an existing control, create a control that combines existing controls, or create a new control from scratch.

Tip

Custom controls are also often called “custom server controls” or even just “server controls.” However, to keep the distinction between the ASP.NET server controls that are a part of .NET and the controls created in this chapter, we’ll keep referring to them as “custom controls.”

Composite controls are most similar to user controls. The key difference being that composite controls are compiled into a dynamic link library (DLL) and you use them as you would any ASP.NET server or user control.

To get started, you’ll create a project in which you’ll create the various custom controls for this chapter. Open the C15_UserControls website in VS2008 and right-click the solution at the top of the tree in the Solution Explorer. Select File → Add → New Project. In the New Project dialog box, select Visual C# Projects, then Web, and then ASP.NET Server Control from the project templates. Name the project CustomControls, as shown in Figure 15-6, and click OK.

Tip

In VS2005, this project type was called Web Control Library and was found in the Windows category. Fortunately, this has been amended in VS2008, although the actual project template file ...