public void MouseMoveHandler(object sender, MouseEventArgs e) { if (e.LeftButton == MouseButtonState.Pressed) { System.Windows.Point pos = e.GetPosition((Canvas)sender); MainWindow mv = Application.Current.Windows.OfType <MainWindow>().FirstOrDefault(); Line line = DrawCanvas.NewLine(currentPoint.X, currentPoint.Y, pos.X, pos.Y, ForegroundLineMarker, mv.CanvasDraw); currentPoint = pos; LineMarkers.Add(line); } }