登录验证码

　　　　 //// <summary>
        /// 生成验证码
        /// </summary>
        /// <param name="length">指定验证码的长度</param>
        /// <returns></returns>
        public static string CreateValidateCode(int length)
        {
            int[] randMembers = new int[length];
            int[] validateNums = new int[length];
            string validateNumberStr = "";
            //生成起始序列值
            int seekSeek = unchecked((int)DateTime.Now.Ticks);
            Random seekRand = new Random(seekSeek);
            int beginSeek = (int)seekRand.Next(0, Int32.MaxValue - length * 10000);
            int[] seeks = new int[length];
            for (int i = 0; i < length; i++)
            {
                beginSeek += 10000;
                seeks[i] = beginSeek;
            }
            //生成随机数字
            for (int i = 0; i < length; i++)
            {
                Random rand = new Random(seeks[i]);
                int pownum = 1 * (int)Math.Pow(10, length);
                randMembers[i] = rand.Next(pownum, Int32.MaxValue);
            }
            //抽取随机数字
            for (int i = 0; i < length; i++)
            {
                string numStr = randMembers[i].ToString();
                int numLength = numStr.Length;
                Random rand = new Random();
                int numPosition = rand.Next(0, numLength - 1);
                validateNums[i] = Int32.Parse(numStr.Substring(numPosition, 1));
            }
            //生成验证码
            for (int i = 0; i < length; i++)
            {
                validateNumberStr += validateNums[i].ToString();
            }
            return validateNumberStr;
        }

        /// <summary>
        /// 根据输入的验证码创建验证码图片
        /// </summary>
        /// <param name="chkCode">验证码字符</param>
        /// <returns></returns>
        public static byte[] CreateValidateCodePic(string chkCode)
        {
            //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", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU", "Impact" };
            Bitmap bmp = new Bitmap(100, 40);
            Graphics g = Graphics.FromImage(bmp);
            g.Clear(Color.White);
            Random rnd = new Random();
            //画噪线 
            for (int i = 0; i < 10; i++)
            {
                int x1 = rnd.Next(100);
                int y1 = rnd.Next(40);
                int x2 = rnd.Next(100);
                int y2 = rnd.Next(40);
                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, 18);
                Color clr = color[rnd.Next(color.Length)];
                g.DrawString(chkCode[i].ToString(), ft, new SolidBrush(clr), (float)i * 20 + 8, (float)8);
            }
            //画噪点 
            for (int i = 0; i < 100; i++)
            {
                int x = rnd.Next(bmp.Width);
                int y = rnd.Next(bmp.Height);
                Color clr = color[rnd.Next(color.Length)];
                bmp.SetPixel(x, y, clr);
            }

            //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();

            }
            finally
            {
                //显式释放资源 
                bmp.Dispose();
                g.Dispose();
            }
        }        

        /// <summary>
        /// 创建验证码字符
        /// </summary>
        /// <param name="length">验证码长度</param>
        /// <returns></returns>
        public string CreateValidateCode(int length)
        {
            string code = qdatmUtils.CreateValidateCode(length);
            return code;
        }

        /// <summary>
        /// 创建验证码图片
        /// </summary>
        /// <param name="code">图片中的验证码字符</param>
        /// <returns></returns>
        public byte[] CreateValidateCodePic(string code)
        {
            var bytes = qdatmUtils.CreateValidateCodePic(code);
            return bytes;
        }

        /// <summary>
        /// 生成验证码
        /// </summary>
        /// <returns></returns>
        public ActionResult CheckCode()
        {
            string code = CreateValidateCode(4);
            Session["ValidateCode"] = code;
            byte[] bytes = CreateValidateCodePic(code);
            return File(bytes, @"image/png");
        }    

        /// <summary>
        /// 验证码验证
        /// </summary>
        /// <param name="code"></param>
        [HttpPost]
        public ContentResult CheckCode(string code)
        {
            bool flag = Session["ValidateCode"].ToString().ToUpper().Equals(code.ToUpper());
            if (flag)
            {
                return Content("true");
            }
            else
            {
                return Content("false");
            }
        }

前台代码：

<div class="input-group" style="display:none" id="vcode">
    <input type="text" class="" name="ValidateCode" id="ValidateCode" placeholder="验证码" required maxlength="10">
    <img src="/Account/CheckCode?ID=1" id="imgCode" alt="单击可刷新" onclick="ClickRemoveChangeCode()" />
</div>

js：

function ClickRemoveChangeCode() {
            var code = $("#imgCode").attr("src");
            $("#imgCode").attr("src", code + "1");
            $("#ValidateCode").val("");
        }
$(document).ready(function () {
            $('#loginForm').validate({
                rules: {
                    ValidateCode: {
                        required: true,
                        maxlength: 4,
                        remote: {
                            url: "/Account/CheckCode",
                            type: "post",
                            dataType: "json",
                            data: { code: function () { return $("#ValidateCode").val(); } }
                        }
                    }
                },
                messages: {
                    ValidateCode: {
                        required: "验证码不能为空",
                        maxlength: "最大长度4个字符",
                        remote: "验证码错误"
                    }
                }

 创建带字母的验证码：

/// <summary>
        /// 创建验证码字母
        /// </summary>
        /// <param name="length">验证码的长度</param>
        /// <returns></returns>
        public static string CreateValidateCode(int length = 4)
        {
            string chkCode = string.Empty;

            //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', '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 < length; i++)
            {
                chkCode += character[rnd.Next(character.Length)];
            }
            return chkCode;
        }

 

来源：https://www.cnblogs.com/MrZheng/p/6407805.html