asp.net驗證碼程序代碼

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Drawing;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class ImgCode : System.Web.UI.Page
{

     private void Page_Load(object sender, System.EventArgs e)
     {
         // 在此處放置用戶代碼以初始化頁面
         this.CreateCheckCodeImage(GenerateCheckCode());
     }

     #region Web 窗體設計器生成的代碼
     override protected void OnInit(EventArgs e)
     {
         //
         // CODEGEN: 該調用是 ASP.NET Web 窗體設計器所必需的。
         //
         InitializeComponent();
         base.OnInit(e);
     }

     /// <summary>
     /// 設計器支持所需的方法 - 不要使用代碼編輯器修改
     /// 此方法的內容。
     /// </summary>
     private void InitializeComponent()
     {
         this.Load += new System.EventHandler(this.Page_Load);
     }
     #endregion
     private string GenerateCheckCode()
     {
         int number;
         char code;
         string checkCode = String.Empty;

         System.Random random = new Random();

         for (int i = 0; i < 5; i++)
         {
             number = random.Next();

             if (number % 2 == 0)
                 code = (char)('0' + (char)(number % 10));
             else
                 code = (char)('A' + (char)(number % 26));

             checkCode += code.ToString();
         }
         Session["CheckCode"] = checkCode;
         //Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

         return checkCode;
     }
     private void CreateCheckCodeImage(string checkCode)
     {
         if (checkCode == null || checkCode.Trim() == String.Empty)
             return;

         System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
         Graphics g = Graphics.FromImage(image);

         try
         {
             //生成隨機生成器
             Random random = new Random();

             //清空圖片背景色
             g.Clear(Color.White);

             //畫圖片的背景噪音線
             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 System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
             System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
             g.DrawString(checkCode, font, brush, 2, 2);

             //畫圖片的前景噪音點
             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()));
             }

             //畫圖片的邊框線
             g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

             System.IO.MemoryStream ms = new System.IO.MemoryStream();
             image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
             Response.ClearContent();
             Response.ContentType = "image/Gif";
             Response.BinaryWrite(ms.ToArray());
         }
         finally
         {
             g.Dispose();
             image.Dispose();
         }
     }
}