Drag and drog Object from drawing area to listview control
You did not say, but I assume that the said ListView control (or whatever control, for that matter) is on a modeless form/window of your AutoCAD add-in. To make things simple, assume it is a Win form ListView.
It is rather simple to let a Win form control accept drag & drop: set its AllowDrop property to True, and handle its DragEnter/DragOver/DragLeave/DragDrop event. Usually, DragEnter and DragDrop would be enough: in DragEnter, you can set DragDropEffect, so that the cursor indicates something useful being dragged to the control; in DragDrop you retrieve the data from DragEventArgs, and do things accordingly. In your case, you want to list entities' information in the Listview, so you have to be able to obtain meaningful data from the DragEventArgs, which is something not easy to do, or not doable by us, .NET API programmers, at all, because if you click (select) a few entities, and drag them, the data in DragEventArgs has a data format named as "AutoCAD Rxx", and the real data is binary in MemoryStream, which we do not know what kind of object/class the binaries can be deserialized back.
However, just think how one start dragging entities in AutoCAD editor: there must be one or more entities have already been selected when the drag begins. So, we can forget the data in DragEventArgs. IN the DragDrop event handler, simply test if AutoCAD has implied SelectionSet, if yes, use it to obtain entities' data and populate the list view.
However, with all said, I do not think dragging from AutoCAD editor to a form is a good user interaction with AutoCAD: if the drag & drop relies on implied selection set, then why use has to drag (by holding a mouse key while moving the mouse to a location on screen)? you can simply provide a button on the UI, which is enabled if implied selection set is not empty, and disable when empty, and simply one click, the form is filled/updated. One click is much more easier than drag. Or you can even make your UI fill up/update automatically when user simply select/deselect entities (or certain entities), just like the "Properties" window. Considering, how entities are selected in AutoCAD editor by default, dragging them to populate another UI would not be welcome by AutoCAD users, I think.
