/// <summary>
/// 图片验证码
/// </summary>
public ActionResult Validate()
{
Bitmap bmp = new Bitmap(80, 40);
Graphics g = Graphics.FromImage(bmp);
SolidBrush sb = new SolidBrush(ValidateCodeHelper.GetColor());
var code = ValidateCodeHelper.BuildCode(4);
CookieHelper.SetCookie("Validate", code, DateTime.Now.AddMinutes(5));
g.DrawString(code, new Font("宋体", 20), sb, 0, 0);
MemoryStream ms = new MemoryStream();
bmp.Save(ms, ImageFormat.Png);
return(File(ms.GetBuffer(), "application/x-png"));
}