ASP.NET MVC实现验证码功能

asp.net MVC
前台
<img id="vcodeimg" src="/Home/VCode" width="70"
                                    height="25" />
                                <span
                                    style="cursor: pointer; text-decoration: underline">换一张</span>
控制器
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
    }
}

验证码类
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.zzzyk.com
            Pen blackPen = new Pen(Color.LightGray, 0);
            for (int i = 0; i < 50; i++)
            {

补充：Web开发 , ASP.Net ,