OnChange example for C++ Builder
Typically, you would use this event to flag changed image data and prompt the user to save the changes before closing a window or exiting an application. That use of the event cannot be tested properly without writing a complete application; so this example just shows you a simple test of the event.
void __fastcall TForm1::Lead1Change (TObject *Sender)
{
ShowMessage("Image data has changed");
}