void WhenDragDrop(DragEventArgs e) { if (null == _manager) { return; } var point = treeView1.PointToClient(new Point(e.X, e.Y)); var node = treeView1.GetNodeAt(point); if (null == node) { return; } if (node.Tag is ProjectId) { var data = (string)e.Data.GetData(DataFormats.StringFormat); _manager.DropToProject(data, (ProjectId)node.Tag); } }