For context sensitive help, we can add a help (?) button to windows title bar, which is a small button with a question mark appears in the caption bar to the left of the Close button. We need to create an event handler for the HelpRequested event of the Control class to display Help information to the user when the Help button of the form is clicked. Then user can drag to the control on windows forms and invoke the context sensitive help.

The value of the HelpButton property is ignored if the Maximize or Minimize buttons are shown. Actually the Help icon is only there when HelpButton is set to True and MaximizeBox and MimizeBox are both set to False. When FormBorderStyle of a dialog is set to FixedToolWindow, the Maximize or Minimize buttons are not shown although they are set to true. In this case, they have to be set to false otherwise the HelpButton won’t be shown.