ActiveX technology includes a powerful mechanism for transferring data within and among Microsoft Windows-based applications. The COM IDataObject interface is the key element of what is known as Uniform Data Transfer. As you'll see, Uniform Data Transfer (UDT) gives you all sorts of options for the formatting and storage of your transferred data, going well beyond standard clipboard transfers.
Microsoft Foundation Class support is available for Uniform Data Transfer, but MFC's support for UDT is not so high-level as to obscure what's going on at the COM interface level. One of the useful applications of UDT is OLE Drag and Drop. Many developers want to use drag-and-drop capabilities in their applications, and drag-and-drop support means that programs now have a standard for information interchange. The MFC library supports drag-and-drop operations, and that, together with clipboard transfer, is the main focus of this chapter.