public class ValidateCode

    {

        /// <summary>

        /// 產生圖形驗證碼。

        /// </summary>

        /// <param name="Code">傳出驗證碼。</param>

        /// <param name="CodeLength">驗證碼字元數。</param>

        /// <param name="Width"></param>

        /// <param name="Height"></param>

        /// <param name="FontSize"></param>

        /// <returns></returns>

        public static byte[] CreateValidateGraphic(out String Code, int CodeLength, int Width, int Height, int FontSize)

        {

            String sCode = String.Empty;

            //顏色列表，用於驗證碼、噪線、噪點

            Color[] oColors ={

             System.Drawing.Color.Black,

             System.Drawing.Color.Red,

             System.Drawing.Color.Blue,

             System.Drawing.Color.Green,

             System.Drawing.Color.Orange,

             System.Drawing.Color.Brown,

             System.Drawing.Color.Brown,

             System.Drawing.Color.DarkBlue

            };

            //字體列表，用於驗證碼

            string[] oFontNames = { "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU", "Impact" };

            //驗證碼的字元集，去掉了一些容易混淆的字元

            char[] oCharacter = {

       '2','3','4','5','6','8','9',

       'A','B','C','D','E','F','G','H','J','K', 'L','M','N','P','R','S','T','W','X','Y'

      };

            Random oRnd = new Random();

            Bitmap oBmp = null;

            Graphics oGraphics = null;

            int N1 = 0;

            System.Drawing.Point oPoint1 = default(System.Drawing.Point);

            System.Drawing.Point oPoint2 = default(System.Drawing.Point);

            string sFontName = null;

            Font oFont = null;

            Color oColor = default(Color);

            //生成驗證碼字串

            for (N1 = 0; N1 <= CodeLength - 1; N1++)

            {

                sCode += oCharacter[oRnd.Next(oCharacter.Length)];

            }

            oBmp = new Bitmap(Width, Height);

            oGraphics = Graphics.FromImage(oBmp);

            oGraphics.Clear(System.Drawing.Color.White);

            try

            {

                for (N1 = 0; N1 <= 4; N1++)

                {

                    //畫噪線

                    oPoint1.X = oRnd.Next(Width);

                    oPoint1.Y = oRnd.Next(Height);

                    oPoint2.X = oRnd.Next(Width);

                    oPoint2.Y = oRnd.Next(Height);

                    oColor = oColors[oRnd.Next(oColors.Length)];

                    oGraphics.DrawLine(new Pen(oColor), oPoint1, oPoint2);

                }

                float spaceWith = 0, dotX = 0, dotY = 0;

                if (CodeLength != 0)

                {

                    spaceWith = (Width - FontSize * CodeLength - 10) / CodeLength;

                }

                for (N1 = 0; N1 <= sCode.Length - 1; N1++)

                {

                    //畫驗證碼字串

                    sFontName = oFontNames[oRnd.Next(oFontNames.Length)];

                    oFont = new Font(sFontName, FontSize, FontStyle.Italic);

                    oColor = oColors[oRnd.Next(oColors.Length)];

                    dotY = (Height - oFont.Height) / 2 + 2;//中心下移2像素

                    dotX = Convert.ToSingle(N1) * FontSize + (N1 + 1) * spaceWith;

                    oGraphics.DrawString(sCode[N1].ToString(), oFont, new SolidBrush(oColor), dotX, dotY);

                }

                for (int i = 0; i <= 30; i++)

                {

                    //畫噪點

                    int x = oRnd.Next(oBmp.Width);

                    int y = oRnd.Next(oBmp.Height);

                    Color clr = oColors[oRnd.Next(oColors.Length)];

                    oBmp.SetPixel(x, y, clr);

                }

                Code = sCode;

                //保存图片数据

                MemoryStream stream = new MemoryStream();

                oBmp.Save(stream, ImageFormat.Jpeg);

                //输出图片流

                return stream.ToArray();

            }

            finally

            {

                oGraphics.Dispose();

            }

        }

    }

public class ValidateCodeController : Controller

    {

        public ActionResult GetImg()

        {

            int width = ConverterHelper.ObjToInt(Request.Params["width"], 100);

            int height = ConverterHelper.ObjToInt(Request.Params["height"], 40);

            int fontsize = ConverterHelper.ObjToInt(Request.Params["fontsize"], 20);

            string code = string.Empty;

            byte[] bytes = ValidateCode.CreateValidateGraphic(out code, 4, width, height, fontsize);

            SessionHelper.SetValiCode(code);

            return File(bytes, @"image/jpeg");

        }

    }

<img id="GL_StandardCode"  style="cursor: pointer;" src="@Url.Action("GetImg", "ValidateCode")?t=@DateTime.Now.Ticks" title="看不清，点击换一张" />

            $("#GL_StandardCode").click(function () {

                var newSrc = "@Url.Action("GetImg", "ValidateCode")" + "?t=" + (new Date()).getTime();

                this.src=newSrc;

                return false;

            });

 string pCode = Request.Params["GL_CodeInput"];

        string sCode = SessionHelper.GetValiCode();

        if (string.IsNullOrEmpty(pCode))

        {

            resultMsg = "请输入验证码";

        }

        else if (string.IsNullOrEmpty(sCode))

        {

            resultMsg = "验证码过期";

        }

        else if (pCode.ToLower() != sCode.ToLower())

        {

            resultMsg = "验证码不正确";

        }