ASP.NET MVC验证码功能实现代码

<img id="vcodeimg" src="/home/vcode" width="70"
                                    height="25" />
                                 <span
                                    style="cursor: pointer; text-decoration: underline">换一张</span>

using system;
using system.collections.generic;
using system.linq;
using system.web;
using system.web.mvc;
using utility;
using jellal**;
namespace sjlwebsite.controllers
{
    public class commoncontroller : controller
    {
        #region 验证码
        [outputcache(duration = 0)]
        public actionresult vcode()
        {
            string code = validatecode.createrandomcode(4);
            session["vcode"] = code;
            validatecode.createimage(code);
            return view();
        }

        public string getcode()
        {
            return session["vcode"].tostr();
        }
        #endregion
    }
}

using system;
using system.collections;
using system.componentmodel;
using system.data;
using system.drawing;
using system.web;
using system.web.sessionstate;
using system.web.ui;
using system.web.ui.webcontrols;
using system.web.ui.htmlcontrols;
namespace utility
{
    ///  <summary> 
    ///  完美随机验证码  0.10 
    ///  verion:0.10 
    ///  description:随机生成设定验证码，并随机旋转一定角度，字体颜色不同 
    ///  </summary> 
    public class validatecode
    {

        ///  <summary> 
        ///  生成随机码 
        ///  </summary> 
        ///  <param  name="length">随机码个数www.52mvc.com</param> 
        ///  <returns></returns> 
        public static string createrandomcode(int length)
        {
            int rand;
            char code;
            string randomcode = string.empty;
            //生成一定长度的验证码 
            system.random random = new random();
            for (int i = 0; i < length; i++)
            {
                rand = random.next();
                if (rand % 3 == 0)
                {
                    code = (char)('a' + (char)(rand % 26));
                }
                else
                {
                    code = (char)('0' + (char)(rand % 10));
                }
                randomcode += code.tostring();
            }
            return randomcode;
        }
        ///  <summary> 
        ///  创建随机码图片 
        ///  </summary> 
        ///  <param  name="randomcode">随机码</param> 
        public static void createimage(string randomcode)
        {
            int randangle = 45; //随机转动角度 
            int mapwidth = (int)(randomcode.length * 23);
            bitmap map = new bitmap(mapwidth, 28);//创建图片背景 
            graphics graph = graphics.fromimage(map);
            graph.clear(color.aliceblue);//清除画面，填充背景 
            graph.drawrectangle(new pen(color.black, 0), 0, 0, map.width - 1, map.height - 1);//画一个边框 
            //graph.smoothingmode = system.drawing.drawing2d.smoothingmode.antialias;//模式 
            random rand = new random();
            //背景噪点生成    www.jb51.net
            pen blackpen = new pen(color.lightgray, 0);
            for (int i = 0; i < 50; i++)
            {
                int x = rand.next(0, map.width);
                int y = rand.next(0, map.height);
                graph.drawrectangle(blackpen, x, y, 1, 1);
            }
            //验证码旋转，防止机器识别   
            char[] chars = randomcode.tochararray();//拆散字符串成单字符数组 
            //文字距中 
            stringformat format = new stringformat(stringformatflags.noclip);
            format.alignment = stringalignment.center;
            format.linealignment = stringalignment.center;
            //定义颜色 
            color[] c = { color.black, color.red, color.darkblue, color.green, color.orange, color.brown, color.darkcyan, color.purple };
            //定义字体 
            string[] font = { "verdana", "microsoft sans serif", "comic sans ms", "arial", "宋体" };
            for (int i = 0; i < chars.length; i++)
            {
                int cindex = rand.next(7);
                int findex = rand.next(5);
                font f = new system.drawing.font(font[findex], 13, system.drawing.fontstyle.bold);//字体样式(参数2为字体大小) 
                brush b = new system.drawing.solidbrush(c[cindex]);
                point dot = new point(16, 16);
                //graph.drawstring(dot.x.tostring(),fontstyle,new solidbrush(color.black),10,150);//测试x坐标显示间距的 
                float angle = rand.next(-randangle, randangle);//转动的度数 
                graph.translatetransform(dot.x, dot.y);//移动光标到指定位置 
                graph.rotatetransform(angle);
                graph.drawstring(chars.tostring(), f, b, 1, 1, format);
                //graph.drawstring(chars.tostring(),fontstyle,new solidbrush(color.blue),1,1,format); 
                graph.rotatetransform(-angle);//转回去 
                graph.translatetransform(2, -dot.y);//移动光标到指定位置 
            }
            //graph.drawstring(randomcode,fontstyle,new solidbrush(color.blue),2,2); //标准随机码 
            //生成图片 
            system.io.memorystream ms = new system.io.memorystream();
            map.save(ms, system.drawing.imaging.imageformat.gif);
            httpcontext.current.response.clearcontent();
            httpcontext.current.response.contenttype = "image/gif";
            httpcontext.current.response.binarywrite(ms.toarray());
            graph.dispose();
            map.dispose();
        }

    }
}