System.Drawing DrawLines

Question

xPanel.Save（ms，System.Drawing.Imaging.ImageFormat.Png）;应该保存在内存流ms中，绘制的每一行显示9个省略号。在下面没有输出png只是一个objGraphicPanel.FillRectangle屏幕。 缺少的是＆＃34; F＆＃34;在PointF x1中，y1，x2和y2是单个浮点数。

 protected void Page_Load(object sender, EventArgs e)
 {
    ...
    using (Bitmap xPanel = new Bitmap(500, 500))
    {
        using (Graphics objGraphicPanel = Graphics.FromImage(xPanel))
        {
            //Background White
            SolidBrush whiteBrush = new SolidBrush(Color.White);
            objGraphicPanel.FillRectangle(whiteBrush, 0, 0, 200, 200);
            Pen colorPen = new Pen(Color.Black, 2);
            MemoryStream ms = new MemoryStream();

            for (k = 1; k <= 9; k++)
            {
                for (int nn = 2; nn <= n; nn++)
                {
                    float x1 = Convert.ToSingle(XYecl[k, nn - 1]);
                    float y1 = Convert.ToSingle(ZYecl[k, nn - 1]);
                    float x2 = Convert.ToSingle(XYecl[k, nn]);
                    float y2 = Convert.ToSingle(ZYecl[k, nn]);
                    PointF[] ptf =
                    {
                        new PointF(x1, y1),
                        new PointF(x2, y2)
                    };
                    objGraphicPanel.DrawLines(colorPen, ptf);
                    xPanel.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
                }
            }
            string Imgbase64 = Convert.ToBase64String(ms.ToArray());
            MyImage.Src = "data:image/png;base64," + Imgbase64;
            objGraphicPanel.Dispose();
        }
        xPanel.Dispose();
    }

 <img ID="MyImage" runat="server" />