C#工具:ASP.NET MVC生成图片验证码

1、复制下列代码，拷贝到控制器中。

#region  生成验证码图片
        // [outputcache(location = outputcachelocation.none, duration = 0, nostore = false)]
        public actionresult securitycode()
        {

            string oldcode = session["securitycode"] as string;
            string code = createrandomcode(5);
            session["securitycode"] = code;
            return file(createvalidategraphic(code), "image/jpeg");
        }


        private byte[] createimage(string checkcode)
        {
            int iwidth = (int)(checkcode.length * 12);
            system.drawing.bitmap image = new system.drawing.bitmap(iwidth, 20);
            graphics g = graphics.fromimage(image);
            font f = new system.drawing.font("arial", 10, system.drawing.fontstyle.bold);
            brush b = new system.drawing.solidbrush(color.white);
            g.clear(color.blue);
            g.drawstring(checkcode, f, b, 3, 3);
            pen blackpen = new pen(color.black, 0);
            random rand = new random();
            for (int i = 0; i < 5; i++)
            {
                int x1 = rand.next(image.width);
                int x2 = rand.next(image.width);
                int y1 = rand.next(image.height);
                int y2 = rand.next(image.height);
                g.drawline(new pen(color.silver, 1), x1, y1, x2, y2);
            }
            system.io.memorystream ms = new system.io.memorystream();
            image.save(ms, system.drawing.imaging.imageformat.jpeg);
            return ms.toarray();
        }

        private string createrandomcode(int codecount)
        {
            string allchar = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z";
            string[] allchararray = allchar.split(',');
            string randomcode = "";
            int temp = -1;
            random rand = new random();
            for (int i = 0; i < codecount; i++)
            {
                if (temp != -1)
                {
                    rand = new random(i * temp * ((int)datetime.now.ticks));
                }
                int t = rand.next(35);
                if (temp == t)
                {
                    return createrandomcode(codecount);
                }
                temp = t;
                randomcode += allchararray[t];
            }
            return randomcode;
        }
        /// <summary>
        /// 创建验证码的图片
        /// </summary>
        public byte[] createvalidategraphic(string validatecode)
        {
            bitmap image = new bitmap((int)math.ceiling(validatecode.length * 16.0), 27);
            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", 13, (fontstyle.bold | fontstyle.italic));
                lineargradientbrush brush = new lineargradientbrush(new rectangle(0, 0, image.width, image.height),
                 color.blue, color.darkred, 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();
            }
        }
        #endregion

2、复制以下图片标记到视图中

<img src="/控制器的名字/securitycode" onclick="this.src+='?new date()'" />

3、验证方式，使用 session["securitycode"] 判断填写的是否相等，txtcode自己输入的验证码。

    　　　　　　　if (session["securitycode"] .tostring().tolower() != txtcode.tolower())
                {
                    response.write("<script>alert('验证码错误')</script>");
                }
                else
                {
                 
                }