After you have created a basic design-time object, you can use features described in this section to provide optional support for toolbox items. If your visual designer supports designer toolbox features, it must implement IDesignerToolbox. To support Drag&Drop, you should implement IDropTarget. To support Click&Drag, you should maintain a pointer to IDesignerToolboxSite. CComDesignerToolbox, IDesignerToolboxImpl, and IDesignerDropTargetImpl provide all these features for you.
Step 1: Request Toolbox Support
Step 2: Set Up the Toolbox Item Map