If your file types are printable, include a Print verb entry in the shell subkey under HKEY_CLASSES_ROOT, following the conventions described in the previous section. This will display the Print command on the pop-up menu for the icon and on the File menu of the folder in which the icon resides when the user selects the icon. When the user chooses the Print command, the system uses the registry entry to determine what application to run to print the file.
Also register a Print To registry entry for the file types your application supports. This entry enables dragging and dropping of a file onto a printer icon. Although a Print To command is not displayed on any menu, the printer includes Print Here as the default command on the pop-up menu displayed when the user drag and drops a file on the printer using button 2.
In both cases, print the file, preferably, without opening the application's primary window. One way to do this is to provide a command-line switch that runs the application for handling the printing operation only (for example, WordPad.exe /p). In addition, display some form of user feedback that indicates whether a printing process has been initiated and, if so, its progress. For example, this feedback could be a modeless message box that displays, "Printing page m of n on printer name" and a Cancel button. You may also include a progress indicator control.