代码修改后的版本，全部提交

Mtxfw.shop/CheckCode.ashx.cs

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+using System;
+using System.Collections.Generic;
+using System.Web;
+using System.Web.Security;
+using System.Web.SessionState;
+using System.Drawing;
+using System.Drawing.Imaging;
+
+
+namespace Mtxfw.shop
+{
+    /// <summary>
+    /// 验证码 by Telesa 2011.04.07
+    /// </summary>
+    public class CheckCode : IHttpHandler, IRequiresSessionState
+    {
+        public void ProcessRequest(HttpContext context)
+        {
+            System.Web.HttpCookie hc = new HttpCookie("code");
+            hc.Value = RandNum(4);
+            System.Web.HttpContext.Current.Response.Cookies.Add(hc);
+
+            ValidateCode(hc.Value, 60, 25, "Arial", 12, "#FFFFFF");
+        }
+
+        /// <summary>
+        /// 生成指定位数的随机数
+        /// </summary>
+        /// <param name="VcodeNum">参数是随机数的位数</param>
+        /// <returns>返回一个随机数字符串</returns>
+        public string RandNum(int VcodeNum)
+        {
+            string Vchar = "0,1,2,3,4,5,6,7,8,9";
+            string[] VcArray = Vchar.Split(','); //拆分成数组
+            string VNum = "";
+            int temp = -1; //记录上次随机数值，尽量避避免生产几个一样的随机数
+
+            Random rand = new Random();
+            //采用一个简单的算法以保证生成随机数的不同
+            for (int i = 0; i < VcodeNum; i++)
+            {
+                if (temp != -1)
+                {
+                    rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
+                }
+
+                int t = rand.Next(VcArray.Length - 1);
+                if (temp != -1 && temp == t)
+                {
+                    return RandNum(VcodeNum);
+                }
+                temp = t;
+                VNum += VcArray[t];
+            }
+            return VNum;
+        }
+
+        /// <summary>
+        /// 生成图片并写入字符
+        /// </summary>
+        /// <param name="VNum">目标字符</param>
+        /// <param name="w">宽</param>
+        /// <param name="h">高</param>
+        /// <param name="font">字体文件</param>
+        /// <param name="fontSize">字体大小</param>
+        /// <param name="bgColor">图片背景颜色</param>
+        private void ValidateCode(string VNum, int w, int h, string font, int fontSize, string bgColor)
+        {
+            //生成图像的实例
+            Bitmap Img = new Bitmap(w, h);
+            //从Img对象生成新的Graphics对象
+            Graphics g = Graphics.FromImage(Img);
+            //背景颜色
+            g.Clear(ColorTranslator.FromHtml(bgColor));
+            //生成Font类的实例
+            Font f = new Font(font, fontSize, FontStyle.Italic|FontStyle.Bold);
+            
+            //生成笔刷类的实例
+            SolidBrush s = new SolidBrush(Color.Red);
+            //将VNum写入图片中
+            g.DrawString(VNum, f, s, 3, 3);
+            //将此图像以Jpeg图像文件的格式保存到流中
+            Img.Save(System.Web.HttpContext.Current.Response.OutputStream, ImageFormat.Jpeg);
+            System.Web.HttpContext.Current.Response.ContentType = "image/Jpeg";
+
+            g.Dispose();
+            Img.Dispose();
+            System.Web.HttpContext.Current.Response.End();
+        }
+
+        public bool IsReusable
+        {
+            get
+            {
+                return false;
+            }
+        }
+    }
+}