Responds to button clicks.
This method implements the PerformClick method of the IButtonControl interface. The PerformClick method can be used when it is needed, for instance, to raise the Click event. By default, it is called for the button that has focus, or for the default button (if no other button has focus) when the user presses the ENTER or SPACE key. This method is also called when the user presses the ESC key if the button is set as the cancel button. Use the form's AcceptButton and CancelButton properties to specify which buttons on a form should act like default (accept) and cancel buttons respectively.