下面的代码第二次运行报错
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("测试字符串", font, brush, 10, 10);/////运行到这句报参数无效
g.Dispose();
font.Dispose();
brush.Dispose();
nbitmap.Save(context.Server.MapPath("~/upload/cert" + DateTime.Now.ToString("yyyyMMddHHmmssfff") + ".jpg"));
nbitmap.Dispose();
}