Set the ShowCloseButton property to true to enable the close button ('x'). This button is displayed at the right edge of the main menu, if there is no main menu it's hidden. In an MDI application, this button will also be hidden when a child MDI form is maximized.
The image below shows the close button being highlighted:
By default, the close button does not implement any specific functionality. To respond to an end-user clicking on this button, you can handle the
CloseButtonClick event. For instance, you can handle this event to close a currently active window that has no title, etc.