ASP.NET MVC 生成验证码

using System.Web.Mvc;
using System.Drawing;
using System;
using System.Drawing.Imaging;
using Models;
using System.IO;

namespace MvcApp.Controllers
{
    /// <summary>
    /// 用户账户信息
    /// </summary>
    [HandleError]
    public class AccountController : BaseController
    {
        /// <summary>
        /// 获取验证码图片
        /// </summary>
        /// <returns></returns>
        public ActionResult ValidateCode()
        {
            //生成验证码字符
            string vnum = GetByRndNum(4);
            int width = vnum.Length * 17;

            Graphics g = null; //画布
            Bitmap bitmap = new Bitmap(width, 32); //图片
            g = Graphics.FromImage(bitmap);
            g.Clear(Color.White); //设定背景色            

            Font font = new Font("微软雅黑", 16, FontStyle.Bold);
            SolidBrush brush = new SolidBrush(ColorTranslator.FromHtml("#411464"));
            g.DrawString(vnum, font, brush, 1, 1);  //画数字

            // 随机产生干扰线，使图象中的认证码不易被其它程序探测到
            Random random = new Random();
            Pen pen = new Pen(ColorTranslator.FromHtml("lightblue"), 18);
            for (int i = 0; i < 8; i++)
            {
                int x = random.Next(width);
                int y = random.Next(20);
                int xstep = random.Next(6);
                int ystep = random.Next(2);
                g.DrawLine(pen, x + 1, y, x + xstep, y + ystep);
            }

            //画矩形边框
            pen.Width = 1;
            g.DrawRectangle(pen, 0, 0, bitmap.Width - 1, bitmap.Height - 1);

            MemoryStream ms = new MemoryStream();
            bitmap.Save(ms, ImageFormat.Jpeg);

            //也可以直接保存到响应流中
            //Response.ClearContent(); //需要输出图象信息 要修改HTTP头 
            //Response.ContentType = "image/jpeg";
            //bitmap.Save(Response.OutputStream, ImageFormat.Jpeg);

            g.Dispose();
            bitmap.Dispose();
            font.Dispose();
            brush.Dispose();
            pen.Dispose();

            return File(ms.ToArray(), "image/jpeg");
        }

        /// <summary>
        /// 随机生成验证码（数字)
        /// </summary>
        /// <param name="VcodeNum"></param>
        /// <returns></returns>
        public string GetByRndNum(int VcodeNum)
        {
            string VNum = "";
            string VcArray = "0123456789";

            Random rand = new Random();

            for (int i = 0; i < VcodeNum; i++)
            {
                VNum += VcArray[rand.Next(0, 9)];
            }

            Session["__VCode"] = VNum;

            return VNum;
        }
    }
}

附：验证码操作简易封装

using System;
using System.Drawing;
using System.Web;

namespace Utility
{
    public class VerifyCode
    {
        #region 验证码长度(默认6个验证码的长度)
        int length = 4;
        public int Length
        {
            get { return length; }
            set { length = value; }
        }
        #endregion

        #region 验证码字体大小(为了显示扭曲效果，默认40像素，可以自行修改)
        int fontSize = 60;
        public int FontSize
        {
            get { return fontSize; }
            set { fontSize = value; }
        }
        #endregion

        #region 边框补(默认1像素)
        int padding = 2;
        public int Padding
        {
            get { return padding; }
            set { padding = value; }
        }
        #endregion

        #region 是否输出燥点(默认不输出)
        bool chaos = true;
        public bool Chaos
        {
            get { return chaos; }
            set { chaos = value; }
        }
        #endregion

        #region 输出燥点的颜色(默认灰色)
        Color chaosColor = Color.LightGray;
        public Color ChaosColor
        {
            get { return chaosColor; }
            set { chaosColor = value; }
        }
        #endregion

        #region 自定义背景色(默认白色)
        Color backgroundColor = Color.White;
        public Color BackgroundColor
        {
            get { return backgroundColor; }
            set { backgroundColor = value; }
        }
        #endregion

        #region 自定义随机颜色数组
        Color[] colors = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
        public Color[] Colors
        {
            get { return colors; }
            set { colors = value; }
        }
        #endregion

        #region 自定义字体数组
        string[] fonts = { "Arial", "Georgia" };
        public string[] Fonts
        {
            get { return fonts; }
            set { fonts = value; }
        }
        #endregion

        #region 自定义随机码字符串序列(使用逗号分隔)
        string codeSerial = "1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,j,k,m,n,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";
        //string codeSerial = "0,1,2,3,4,5,6,7,8,9";
        public string CodeSerial
        {
            get { return codeSerial; }
            set { codeSerial = value; }
        }
        #endregion

        #region 产生波形滤镜效果

        private const double PI = 3.1415926535897932384626433832795;
        private const double PI2 = 6.283185307179586476925286766559;

        /// <summary>
        /// 正弦曲线Wave扭曲图片（Edit By 51aspx.com）
        /// </summary>
        /// <param name="srcBmp">图片路径</param>
        /// <param name="bXDir">如果扭曲则选择为True</param>
        /// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高，一般为3</param>
        /// <param name="dPhase">波形的起始相位，取值区间[0-2*PI)</param>
        /// <returns></returns>
        public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
        {
            System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);

            // 将位图背景填充为白色
            System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);
            graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);
            graph.Dispose();

            double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;

            for (int i = 0; i < destBmp.Width; i++)
            {
                for (int j = 0; j < destBmp.Height; j++)
                {
                    double dx = 0;
                    dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;
                    dx += dPhase;
                    double dy = Math.Sin(dx);

                    // 取得当前点的颜色
                    int nOldX = 0, nOldY = 0;
                    nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
                    nOldY = bXDir ? j : j + (int)(dy * dMultValue);

                    System.Drawing.Color color = srcBmp.GetPixel(i, j);
                    if (nOldX >= 0 && nOldX < destBmp.Width
                     && nOldY >= 0 && nOldY < destBmp.Height)
                    {
                        destBmp.SetPixel(nOldX, nOldY, color);
                    }
                }
            }

            return destBmp;
        }



        #endregion

        #region 生成校验码图片
        public Bitmap CreateImageCode(string code)
        {
            int fSize = FontSize;
            int fWidth = fSize + Padding;

            int imageWidth = (int)(code.Length * fWidth) + 4 + Padding * 2;
            int imageHeight = fSize * 2 + Padding;

            System.Drawing.Bitmap image = new System.Drawing.Bitmap(imageWidth, imageHeight);

            Graphics g = Graphics.FromImage(image);

            g.Clear(BackgroundColor);

            Random rand = new Random();

            //给背景添加随机生成的燥点以及噪音线
            if (this.Chaos)
            {

                Pen pen = new Pen(ChaosColor, 0);
                int c = Length * 60;

                for (int i = 0; i < c; i++)
                {
                    int x = rand.Next(image.Width);
                    int y = rand.Next(image.Height);

                    g.DrawRectangle(pen, x, y, 1, 1);
                }
                int x1;
                int y1;
                int x2;
                int y2;
                for (int i = 0; i < 15; ++i)
                {
                    x1 = rand.Next(image.Width);
                    y1 = rand.Next(image.Height);
                    x2 = rand.Next(image.Width);
                    y2 = rand.Next(image.Height);
                    g.DrawLine(new Pen(Color.FromArgb(rand.Next(255), rand.Next(255), rand.Next(255))), x1, y1, x2, y2);
                }
            }

            int left = 0, top = 0, top1 = 1, top2 = 1;

            int n1 = (imageHeight - FontSize - Padding * 2);
            int n2 = n1 / 4;
            top1 = n2;
            top2 = n2 * 2;

            Font f;
            Brush b;

            int cindex, findex;

            //随机字体和颜色的验证码字符
            for (int i = 0; i < code.Length; i++)
            {
                cindex = rand.Next(Colors.Length - 1);
                findex = rand.Next(Fonts.Length - 1);

                f = new System.Drawing.Font(Fonts[findex], fSize, System.Drawing.FontStyle.Bold);
                b = new System.Drawing.SolidBrush(Colors[cindex]);

                if (i % 2 == 1)
                {
                    top = top2;
                }
                else
                {
                    top = top1;
                }

                left = i * fWidth;

                g.DrawString(code.Substring(i, 1), f, b, left, top);
            }

            //产生波形（Add By 51aspx.com）
            //image = TwistImage(image, true, 10, rand.NextDouble() * 4 + 2);

            //画一个边框 边框颜色为Color.Gainsboro
            g = Graphics.FromImage(image);
            g.DrawRectangle(new Pen(Color.Gainsboro, 0), 0, 0, image.Width - 1, image.Height - 1);
            g.Dispose();



            return image;
        }
        #endregion

        #region 将创建好的图片输出到页面
        public void CreateImageOnPage(string code, HttpContext context)
        {
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            Bitmap image = this.CreateImageCode(code);

            image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

            context.Response.ClearContent();
            context.Response.Expires = -1;
            context.Response.CacheControl = "no-cache";
            context.Response.ContentType = "image/Jpeg";
            context.Response.BinaryWrite(ms.GetBuffer());

            ms.Close();
            ms = null;
            image.Dispose();
            image = null;
        }
        #endregion

        #region 生成随机字符码
        public string CreateVerifyCode(int codeLen)
        {
            if (codeLen == 0)
            {
                codeLen = Length;
            }

            string[] arr = CodeSerial.Split(',');

            string code = "";

            int randValue = -1;

            Random rand = new Random(unchecked((int)DateTime.Now.Ticks));

            for (int i = 0; i < codeLen; i++)
            {
                randValue = rand.Next(0, arr.Length - 1);

                code += arr[randValue];
            }

            return code;
        }
        public string CreateVerifyCode()
        {
            return CreateVerifyCode(0);
        }
        #endregion
    }
}