Drag & Drop – DropTarget class
§Inherits Autodesk.AutoCAD.Windows.DropTarget
§Override OnDrop
§DocumentLock
The class that is passed into the DoDragDrop function needs to inherit from Autodesk.AutoCAD.Windows.DropTarget and also needs to override the OnDrop function.  In the OnDrop function you define what happens when the drop occurs. In this example a function AddAnEnt of the adskClass is being run. Notice that the active document is being locked by creating a DocumentLock variable. The document  needs to be locked when dragging and dropping if objects are going to be opened in the document. When AddAnEnt is run from a command like was done in previous labs, document locking is taken care of automatically. Because AddAnEnt is going to be opening database objects and is not run from a command, the document needs to be locked or an eLockViolation error would occur. The using, and end using statement with a DocumentLock variable will lock and unlock the document.