/// <summary>
/// 验证码
/// </summary>
/// <returns></returns>
public ActionResult GetVerificationCode()
{
string verificationCode = VerificationCodeHelper.CreateVerificationText(4);
Bitmap _img = VerificationCodeHelper.CreateVerificationImage(verificationCode, 95, 30);
_img.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
TempData["VerificationCode"] = verificationCode.ToUpper();
return(null);
}