Click calls any event handler attached to the OnClick event. Override Click to provide other responses in addition to the inherited event-handler call when the user clicks the control or the application simulates a user click. 

A control calls Click whenever it receives a left mouse-button mouse-up message (WM_LBUTTONUP) if that message indicates that the mouse up occurred near the corresponding mouse-down. Many controls call Click in other circumstances, such as when a user types the shortcut key for a button or menu item. 

DblClick 

OnClick