Subclassing and Hooking with Visual Basic

A Low-Level Hook Example

The following example uses the WH_KEYBOARD_LL hook in a pure VB application, which is shown in Figure 12-5. You do not have to use C++ code to install and use this hook. In fact, in many instances you can substitute this hook for a system-wide WH_KEYBOARD hook; this way, you do not have to use any language other than VB.

Figure 12-5. Screenshot of low-level keyboard hook application

Table 12-3 presents the nondefault properties of the form and its controls.

Table 12-3. Nondefault Properties of the Form and Its Controls

Object Type	Property Name	Property Value
Form	Name	Form2
Form	Caption	“WH_KEYBOARD_LL Hook Application”
Form	BorderStyle	3-Fixed Dialog
Form	Top	420
Form	Left	132
Form	Height	1440
Form	Width	4065
Command Button1	Name	cmdHook
Command Button1	Caption	“hook”
Command Button1	Top	120
Command Button1	Left	1530
Command Button1	Height	315
Command Button1	Width	915
Command Button2	Name	cmdUnHook
Command Button2	Caption	“unhook”
Command Button2	Top	600
Command Button2	Left	1530
Command Button2	Height	315
Command Button2	Width	915

This application sets a system-wide, low-level keyboard hook and discards any DEL key presses. More specifically, it discards the WM_KEYDOWN and WM_KEYUP messages for the DEL key.

To see how this application operates, open up several copies of Notepad or another word ...