public static void RegisterDragAndDrop <FI, DI, FSI>(this ExplorerViewModel <FI, DI, FSI> explorervm, DirectoryTree2 dtree)
            where FI : FSI
            where DI : FSI
        {
            FileDragDropHelper <EntryViewModel <FI, DI, FSI> > .SetEnableDrag(dtree, true);

            FileDragDropHelper <EntryViewModel <FI, DI, FSI> > .SetEnableDrop(dtree, true);

            RegisterConstructMethod(explorervm);
        }
        public static void RegisterDragAndDrop <FI, DI, FSI>(this ExplorerViewModel <FI, DI, FSI> explorervm, FileList2 fileList)
            where FI : FSI
            where DI : FSI
        {
            FileDragDropHelper <EntryViewModel <FI, DI, FSI> > .SetEnableDrag(fileList, true);

            FileDragDropHelper <EntryViewModel <FI, DI, FSI> > .SetEnableDrop(fileList, true);

            RegisterConstructMethod(explorervm);
        }