/// <summary>
/// 验证码 GET: /User/ValidCode/1234
/// </summary>
/// <param name="aid"></param>
/// <returns></returns>
public ActionResult ValidCode(string aid)
{
CaptchaImage ci = CaptchaImage.CreateCaptcha(aid);
using (Bitmap b = ci.RenderImage())
{
b.Save(Response.OutputStream, ImageFormat.Jpeg);
}
Response.ContentType = "image/jpeg";
Response.StatusCode = 200;
Response.StatusDescription = "OK";
return(null);
}