A command must be set for file type '<filetype>'
When specifying a file type in the File Types Editor, you must also specify the application that the file type will be associated with. The Command property of the file type is used to specify an executable file or project output.
To correct this error
In the File Types Editor, select the file type noted in the error message.
In the Properties window, select the Command property and click the ellipsis (...) button to open the Select Item in Project dialog box.
In the Select Item in Project dialog box, select the executable file or project output to be associated with the file type.