private DragDropData CheckFolderOrFile(DragDropViewModel viewModel)
        {
            DragDropData returnData = null;
            if (true == (viewModel is FileViewModel))
            {
                returnData = new DragDropData(viewModel.Data.RelativePath, false);
            }
            else if (true == (viewModel is FolderViewModel))
            {
                returnData = new DragDropData(viewModel.Data.RelativePath, true);
            }

            return returnData;
        }
 private void Update(DragDropData newData)
 {
     this.Sources.Add(newData);
     IsChanged = true;
     OnFocused();
 }
 private void Update(DragDropData newData)
 {
     this.Destinations.Add(newData);
     IsChanged = true;
     OnFocused();
 }