How to make Help in c# ?

If the question is related to the Windows Forms application, then Control.HelpRequested can be used for displaying the context sensitive help. As explained here
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.helprequested.aspx[^]
The HelpRequested event is commonly raised when the user presses the F1 key or an associated context-sensitive help button is clicked
An example is also given at the above reference.

Since, Windows Forms controls are derived from the Control class this event will be available on them.

Regarding using the help button in menu strip or tool bar, a standard button with appropriate help icon can be used and the help can be handled in the click event of this button.

Read the following:

http://stackoverflow.com/questions/1029316/how-to-create-f1-help-in-windows-forms-using-c-sharp[^]

http://stackoverflow.com/questions/1006312/how-to-open-chm-file-on-specified-node-toc-net[^]

http://bytes.com/topic/c-sharp/answers/227251-creating-help-files[^]