Custom Controls

Custom controls are a good example of base code that can be reused time and time again. Tired of having to code a GotFocus event for every text box to highlight its contents? Why not create a custom TextBox control that handles its own GotFocus event but in all other respects acts like a normal text box? The ActiveX Control Interface wizard will generate up to 95 percent of the code you need, leaving you with only a few lines of code to write yourself. A custom control that was generated from this wizard is included with the sample code for this chapter. If you examine the code closely, you will see that the ActiveX Control Interface wizard generated all but four lines!

The sample control is very simple—it simply extends an existing property of another control. However, the wizard makes it equally simple to add custom properties of your own, such as numeric formatting and data validation. For more detailed information on creating custom controls, see Chapter 14. Chapter 6 also provides some information on creating a Year 2000_compliant TextBox control.