我写了一个小程序，应该显示一个椭圆在确切的鼠标位置。问题是，我现在这样做的方式，鼠标和椭圆的位置只在屏幕的中心精确。如果我把鼠标移到离窗口边框更远的地方，它们就会漂得越来越远。
我使用MouseOver元素来更新鼠标位置。

下面是我的代码：

private void Window_MouseMove(object sender, MouseEventArgs e)
{
   Main_Grid.Children.Clear();

   MousePos_Ellipse = new Ellipse();
   Point MousePos_Point = new Point();

   MousePos_Point = Mouse.GetPosition(Main_Grid);

   Main_Grid.Children.Remove(MousePos_Ellipse);

   SolidColorBrush mySolidColorBrush = new SolidColorBrush();

   mySolidColorBrush.Color = Color.FromArgb(55, 255, 255, 0);
   MousePos_Ellipse.Fill = mySolidColorBrush;
   MousePos_Ellipse.StrokeThickness = 2;
   MousePos_Ellipse.Stroke = Brushes.Black;

   // Set the width and height of the Ellipse.
   MousePos_Ellipse.Width = 15;
   MousePos_Ellipse.Height = 15;
   // At this Point I do my Positioning
   MousePos_Ellipse.Margin = new Thickness(left: MousePos_Point.X - ( Main_Grid.ActualWidth / 2)  , top: MousePos_Point.Y - ( Main_Grid.ActualHeight / 2 ), right: 0 , bottom: 0);

    // Add the Ellipse to the Grid
    Main_Grid.Children.Add(MousePos_Ellipse);
}