public void ProcessRequest(HttpContext context)
{
        Bitmap nbitmap = new Bitmap(1000, 1000);
        Graphics g = Graphics.FromImage(nbitmap);

        Font font = new Font(FontFamily.GenericSansSerif, 10, FontStyle.Italic);
        Brush brush = Brushes.Black;
        g.DrawString("測試字串", font, brush, 10, 10);/////執行到這句報引數無效
        g.Dispose();
        font.Dispose();
        brush.Dispose();
        nbitmap.Save(context.Server.MapPath("~/upload/cert" + DateTime.Now.ToString("yyyyMMddHHmmssfff") + ".jpg"));
        nbitmap.Dispose();
}