VB Shell Programming

Dynamic Context Menus

Static context menus are limited because they are the same for every file object of a given type. Also, the number of files that can be processed through a static menu is limited by the program that is used to carry out the command. What if you need to process 20 files? What if you need different processing options based on the state of the file itself? There are also situations where you might need one context menu for a group of files and another for a single file. This is where dynamic context menus come into play.

A context menu handler is an ActiveX DLL that implements two interfaces: IShellExtInit and IContextMenu. A third interface, IDataObject, is required to implement IShellExtInit. It is not implemented by the object itself but exists as a method parameter in IShellExtInit. We’ll explore these interfaces in greater depth after we examine how the shell uses a context menu handler to assemble a context menu.

The process begins when one or more files is right-clicked in Explorer. When this occurs, the shell checks the shellex key under the application identifier key to see if a context menu handler has been defined for the selected file type. In the case of the .rad file, the shell would look under the following key:

HKEY_CLASSES_ROOT/
    radfile/
        shellex/
            ContextMenuHandlers/

If you select 15 files that are of all different types, there is still only one file with active focus: the last file selected in the group. It is this file for which the ...