mvc验证码图片生成

 /// <summary>
    ///生成验证码
    /// </summary>
    public class VerifyCode
    {
        /// <summary>
        /// 生成验证码
        /// </summary>
        /// <returns></returns>
        public byte[] GetVerifyCode()
        {
            int codeW = 80;
            int codeH = 30;
            int fontSize = 16;
            string chkCode = string.Empty;
            //颜色列表，用于验证码、噪线、噪点 
            Color[] color = { Color.Black, Color.Red, Color.Blue, Color.Green, Color.Orange, Color.Brown, Color.Brown, Color.DarkBlue };
            //字体列表，用于验证码 
            string[] font = { "Times New Roman" };
            //验证码的字符集，去掉了一些容易混淆的字符 
            char[] character = { '2', '3', '4', '5', '6', '8', '9', 'a', 'b', 'd', 'e', 'f', 'h', 'k', 'm', 'n', 'r', 'x', 'y', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'R', 'S', 'T', 'W', 'X', 'Y' };
            Random rnd = new Random();
            //生成验证码字符串 
            for (int i = 0; i < 4; i++)
            {
                chkCode += character[rnd.Next(character.Length)];
            }
            //写入Session、验证码加密
            HttpContext.Current.Session("session_verifycode", MD5PassWordProvider.CutMD5(chkCode.ToLower(),16));
            //创建画布
            Bitmap bmp = new Bitmap(codeW, codeH);
            Graphics g = Graphics.FromImage(bmp);
            g.Clear(Color.White);
            //画噪线 
            for (int i = 0; i < 1; i++)
            {
                int x1 = rnd.Next(codeW);
                int y1 = rnd.Next(codeH);
                int x2 = rnd.Next(codeW);
                int y2 = rnd.Next(codeH);
                Color clr = color[rnd.Next(color.Length)];
                g.DrawLine(new Pen(clr), x1, y1, x2, y2);
            }
            //画验证码字符串 
            for (int i = 0; i < chkCode.Length; i++)
            {
                string fnt = font[rnd.Next(font.Length)];
                Font ft = new Font(fnt, fontSize);
                Color clr = color[rnd.Next(color.Length)];
                g.DrawString(chkCode[i].ToString(), ft, new SolidBrush(clr), (float)i * 18, (float)0);
            }
            //将验证码图片写入内存流，并将其以 "image/Png" 格式输出 
            MemoryStream ms = new MemoryStream();
            try
            {
                bmp.Save(ms, ImageFormat.Png);
                return ms.ToArray();
            }
            catch (Exception)
            {
                return null;
            }
            finally
            {
                g.Dispose();
                bmp.Dispose();
            }
        }
    }

//MD5加密
 #region 将普通字符串转成MD5字符串
    /// <summary>
    /// 将普通字符串转成MD5字符串
    /// </summary>
    public static class MD5PassWordProvider
    {
        public static string Hash(string message)
        {
            if (string.IsNullOrEmpty(message))
            {
                return string.Empty;
            }
            else
            {
                MD5 md5 = MD5.Create();
                byte[] source = Encoding.UTF8.GetBytes(message);
                byte[] result = md5.ComputeHash(source);
                StringBuilder buffer = new StringBuilder(result.Length);

                for (int i = 0; i < result.Length; i++)
                {
                    buffer.Append(result[i].ToString("x"));
                }
                return buffer.ToString();
            }
        }
        /// <summary>
        /// MD5加密验证码
        /// </summary>
        public static string CutMD5(string str, int code)
        {
            string strEncrypt = string.Empty;
            if (code == 16)
            {
                strEncrypt = Hash(str).Substring(8, 16);
            }
            return strEncrypt;
        }
    }
    #endregio

mvc中使用

/// <summary>
        /// 生成验证码
        /// </summary>
        [HttpGet]
        public ActionResult VerifyCode()
        {
            return File(new VerifyCode().GetVerifyCode(), @"image/Gif");
        }

cshtml中显示及刷新

<img id="login_verifycode" class="login_verifycode" src="~/Login/VerifyCode" alt="点击切换验证码"
                                 title="点击切换验证码"/>

//样式
.login_verifycode{
    float: right;
    margin-top: 1px;
    display:inline-block;
    text-align:center;
    cursor:pointer;
    width: 100px;
    height: 36px;
    padding-right: 0;
    padding-left: 0;
    /*border: 1px solid #d5d5d5;*/
    font-size: 14px;
    color: #727272;
    background: white;
    margin-left:-4px;
    border-top-right-radius: 5px;
    border-bottom-right-radius: 5px;
}

//js
//点击切换验证码
        $("#login_verifycode").click(function () {
            $("#code").val('');//验证码的输入
            $("#login_verifycode").attr("src", contentPath + "/Login/VerifyCode?time=" + Math.random());
        });