private void CanvasPanel_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
if (IsMultiSelecting)
{
var geometry = new RectangleGeometry(new Rect(SelectionSquareTopLeft, e.GetPosition(CanvasPanel)));
var visualInRegion = CanvasPanel.GetVisuals(geometry);
MessageBox.Show($"选中数量：{visualInRegion.Count}");
IsMultiSelecting = false;
CanvasPanel.RemoveVisual(SelectionSquare);
CanvasPanel.ReleaseMouseCapture();
}
else
{
IsDragging = false;
}
}