public void Create() { Response.ContentType = "image/gif"; CaptchaHelper helper = new CaptchaHelper(); Random r = new Random(); double d = r.NextDouble(); string text = FormsAuthentication.HashPasswordForStoringInConfigFile(d.ToString(), "SHA1"); string vcode = text.Substring(4, 5); Session["CaptchaCode"] = vcode.ToLower(); Session.Timeout = 1; Bitmap capthaBmp = helper.Generate(vcode); capthaBmp.Save(Response.OutputStream, ImageFormat.Gif); }