public ActionResult VCode()
{
//引用的都是程序集。需要生成后才会有效果的。
ValidateCodeHelper vCode = new ValidateCodeHelper();
string code = vCode.CreateValidateCodeContainsLetter(4);
Session["ValidateCode"] = code;
byte[] bytes = vCode.CreateValidateGraphic(code);
return(File(bytes, @"image/jpeg"));
}