Subclassing and Hooking with Visual Basic

Superclassing

Superclassing was introduced in Chapter 4. Basically, superclassing involves creating a new base class -- or superclass -- that we then use to create one or more new superclassed windows. Each superclassed window retains the base class’s properties and window procedure. This allows us to easily create many windows that look and operate similarly.

Due to the object-oriented nature of WinForms, we can easily perform superclassing using VB.NET or, for that matter, any other .NET language. The first step is to create a window that will act as our superclass, as Example 22-6 shows. We will use this superclass window to inherit from and create our own window, as Example 22-7 shows. It is just that simple -- more so than implementing superclassing in a previous version of VB.

The application

The application that we will build to implement superclassing contains two WinForms. The first WinForm, called Form1, is the base, or superclass, WinForm. The second WinForm, called Superclass_Ex, inherits from Form1.

The code for Form1 is taken from the application in Example 22-3. To this code I have added a button that has the caption “Create Wnd”. We will use this button to create new windows from the Superclass_Ex WinForm.

Table 22-4 lists the nondefault properties of the superclass form and its controls. Table 22-5 lists the nondefault properties for the Superclass_Ex WinForm. This form does not contain any controls; all controls are inherited from Form1.

Table 22-4. Nondefault ...