The WindowHandle property provides access to the same window handle as the Handle property, but WindowHandle is protected, and therefore only accessible to code inside the control. 

The advantage to using WindowHandle is that it can be written to, while the Handle property is read-only. Use WindowHandle when implementing methods that need to change the value of the control's window handle. Unlike the Handle property, reading the value of WindowHandle doesn't automatically create a valid handle. Reading WindowHandle can return a zero value. 

Handle 

HandleNeeded