public ValidateCode()
  {

  }

  protected override void OnLoad(EventArgs e)
  {
   CreateValidateImage(length);
  }

  /// <summary>
  /// 創(chuàng)建隨機驗證碼
  /// </summary>
  /// <param name="length">驗證碼長度</param>
  /// <returns></returns>
  public string CreateCode(int length)
  {
   if(length <= 0) return string.Empty;
   ///創(chuàng)建一組隨機數(shù)，并構(gòu)成驗證碼
   Random random = new Random();
   StringBuilder sbCode = new StringBuilder();
   for(int i = 0; i < length; i++)
   {
    sbCode.Append(random.Next(0,10));
   }
   ///保存驗證碼到Session對象中
   code = sbCode.ToString();
   Session[VALIDATECODEKEY] = code;
   return code;
  }

  /// <summary>
  /// 創(chuàng)建驗證碼的圖片和驗證碼
  /// </summary>
  /// <param name="length">驗證碼的長度</param>
  public void CreateValidateImage(int length)
  {   ///創(chuàng)建驗證碼
   code = CreateCode(length);
   ///創(chuàng)建驗證碼的圖片
   CreateValidateImage(code);
  }

  /// <summary>
  /// 創(chuàng)建驗證碼的圖片和驗證碼
  /// </summary>
  /// <param name="code">驗證碼</param>
  public void CreateValidateImage(string code)
  {
   if(string.IsNullOrEmpty(code) == true) return;
   ///保存驗證碼到Session對象中
   Session[VALIDATECODEKEY] = code;
   ///創(chuàng)建一個圖像
   Bitmap image = new Bitmap((int)Math.Ceiling((code.Length * IMAGELENGTHBASE)),IMAGEHEIGTH);
   Graphics g = Graphics.FromImage(image);

   ///隨機數(shù)生成器
   Random random = new Random();

   try
   {
    ///清空圖像，并指定填充顏色
    g.Clear(Color.White);

    ///繪制圖片的干擾線
    int x1,x2,y1,y2;
    for(int i = 0; i < IMAGELINENUMBER; i++)
    {
     x1 = random.Next(image.Width);
     y1 = random.Next(image.Height);
     x2 = random.Next(image.Width);
     y2 = random.Next(image.Height);
     ///繪制干擾線
     g.DrawLine(new Pen(Color.Silver),x1,y1,x2,y2);
    }

    ///繪制驗證碼
    Font font = new Font("Tahoma",12,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(code,font,brush,2.0f,2.0f);

    ///畫圖片的前景噪音點
    int x,y;
    for(int i = 0; i < IMAGEPOINTNUMBER; i++)
    {
     x = random.Next(image.Width);
     y = random.Next(image.Height);
     ///繪制點
     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);
    ///保存圖片的內(nèi)容到流中
    MemoryStream ms = new MemoryStream();
    image.Save(ms,ImageFormat.Gif);
    ///輸出圖片
    Response.ClearContent();
    Response.ContentType = "image/Gif";
    Response.BinaryWrite(ms.ToArray());
   }
   finally
   {   ///釋放占有的資源
    g.Dispose();
    image.Dispose();
   }
  }
 }
}