WPF绘图性能问题

代码：

    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            DrawPanel chart_ = new DrawPanel();
            LineCanvas _mask = new LineCanvas();
            grid1.Children.Add(chart_);
            grid1.Children.Add(_mask);
            chart_.plot();
        }
    }
    public class LineCanvas : Canvas
    {
        public LineCanvas()
        {
            Background = Brushes.Transparent;
            var line = new Line()
            {
                StrokeThickness = 2,
                Stroke = System.Windows.Media.Brushes.Black,
            };

            this.Children.Add(line);
            MouseMove += (send, e) =>
              {
                  Point point = e.GetPosition(this);
                  line.X1 = point.X;
                  line.Y1 = 0;
                  line.X2 = point.X;
                  line.Y2 = ActualHeight;
              };
        }
    }

    public class DrawPanel : Panel
    {
        private DrawingVisual _drawingVisual = new DrawingVisual();
        public DrawPanel()
        {
            this.AddVisualChild(_drawingVisual);
            IsHitTestVisible = false;
        }
        public Pen p = new Pen(Brushes.Gainsboro, 1.0);
        public void plot()
        {
            p.Freeze();
            var dc = _drawingVisual.RenderOpen();
            _drawingVisual.CacheMode = new BitmapCache();//这句话是关键，加了性能直接提升
            for (int x = 0; x < 10000; x++)
            {
                double xx = 700.0 / 2 + ((x / 10000.0) * (700.0 / 2.0));
                Point p1 = new Point(xx, 0);
                Point p2 = new Point(xx, 353);
                dc.DrawLine(p, p1, p2);
            }
            dc.Close();
        }
        protected override int VisualChildrenCount
        {
            get { return 1; }
        }
        protected override Visual GetVisualChild(int index)
        {
            if (index == 0)
                return _drawingVisual;
            throw new IndexOutOfRangeException();
        }
    }