C#生成自定义登录验证码（微信公众号验证码，邮箱验证码等）

本文只讲解自定义验证码生成的实现，其他两种见我其他文章。

在项目上线使用时，网络对外警察后受到攻击，特别是尝试各种密码组合对用户名密码登录的暴力破解，需要增加验证码来增加用户信息的安全性。

ps:注意生成的验证码要具备时效性，设置3-5分钟失效，或登录一次之后失效。

效果图：

代码如下：

<div class="login_form_num">
 <input type="text" placeholder="请输入验证码" class="login_input_imgCode" id="imgCode"/>
 <img src="@Url.Action("CheckCodeSimple", "Login")" id="showimg" class="showimg" alt="单击可刷新" onclick="ClickRemoveChangeCode()"/>
</div>

<script>
      //刷新验证码
     function ClickRemoveChangeCode() {
        var code = $("#showimg").attr("src");
        $("#showimg").attr("src", code+"?id=1");
    }

</script>

        /// <summary>
        /// 生成验证码
        /// </summary>
        /// <returns></returns>
        public ActionResult CheckCodeSimple()
        {
            validateCode vCode = new validateCode();

            string code = vCode.CreateValidateCode(5);

            Session["ValidateCode"] = code;

            byte[] bytes = vCode.CreateValidateGraphic(code);

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

        }

validateCode类

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Text;

namespace Rate.Tools.validateCode
{
    public class validateCode
    {
        public 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;

        }

        public byte[] CreateValidateGraphic(string validateCode)
        {

            Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), 22);

            Graphics g = Graphics.FromImage(image);

            try
            {

                //生成随机生成器

                Random random = new Random();

                //清空图片背景色

                g.Clear(Color.White);

                //画图片的干扰线

                for (int i = 0; i < 25; i++)
                {

                    int x1 = random.Next(image.Width);

                    int x2 = random.Next(image.Width);

                    int y1 = random.Next(image.Height);

                    int y2 = random.Next(image.Height);

                    g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);

                }

                Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));

                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height),

                 Color.Blue, Color.Red, 1.2f, true);

                g.DrawString(validateCode, font, brush, 3, 2);

                //画图片的前景干扰点

                for (int i = 0; i < 100; i++)
                {

                    int x = random.Next(image.Width);

                    int y = random.Next(image.Height);

                    image.SetPixel(x, y, Color.FromArgb(random.Next()));

                }

                //画图片的边框线

                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

                //保存图片数据

                MemoryStream stream = new MemoryStream();

                image.Save(stream, ImageFormat.Jpeg);

                //输出图片流

                return stream.ToArray();

            }

            finally
            {

                g.Dispose();

                image.Dispose();

            }

        }

    }
}