public class ValidCode{  #region Private Fields  private const double PI = 3.1415926535897932384626433832795;  private const double PI2 = 6.283185307179586476925286766559;  //private readonly int _wordsLen = 4;  private int _len;  private CodeType _codetype;  private readonly Single _jianju = (float)18.0;  private readonly Single _height = (float)24.0;  private string _checkCode;  #endregion  #region Public Property  public string CheckCode  {   get   {    return _checkCode;   }  }  #endregion  #region Constructors  /// <summary>  /// public constructors  /// </summary>  /// <param name="len"> 驗證碼長度 </param>  /// <param name="ctype"> 驗證碼類型：字母、數字、字母+ 數字 </param>  public ValidCode(int len, CodeType ctype)  {   this._len = len;   this._codetype = ctype;  }  #endregion  #region Public Field  public enum CodeType { Words, Numbers, Characters, Alphas }  #endregion  #region Private Methods  private string GenerateNumbers()  {   string strOut = "";   System.Random random = new Random();   for (int i = 0; i < _len; i++)   {    string num = Convert.ToString(random.Next(10000) % 10);    strOut += num;   }   return strOut.Trim();  }  private string GenerateCharacters()  {   string strOut = "";   System.Random random = new Random();   for (int i = 0; i < _len; i++)   {    string num = Convert.ToString((char)(65 + random.Next(10000) % 26));    strOut += num;   }   return strOut.Trim();  }  //  private string GenerateAlphas()  {   string strOut = "";   string num = "";   System.Random random = new Random();   for (int i = 0; i < _len; i++)   {    if (random.Next(500) % 2 == 0)    {     num = Convert.ToString(random.Next(10000) % 10);    }    else    {     num = Convert.ToString((char)(65 + random.Next(10000) % 26));    }    strOut += num;   }   return strOut.Trim();  }  private System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)  {   System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);   // 將位圖背景填充為白色   System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);   graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);   graph.Dispose();   double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;   for (int i = 0; i < destBmp.Width; i++)   {    for (int j = 0; j < destBmp.Height; j++)    {     double dx = 0;     dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;     dx += dPhase;     double dy = Math.Sin(dx);     // 取得當前點的顏色     int nOldX = 0, nOldY = 0;     nOldX = bXDir ? i + (int)(dy * dMultValue) : i;     nOldY = bXDir ? j : j + (int)(dy * dMultValue);     System.Drawing.Color color = srcBmp.GetPixel(i, j);     if (nOldX >= 0 && nOldX < destBmp.Width      && nOldY >= 0 && nOldY < destBmp.Height)     {      destBmp.SetPixel(nOldX, nOldY, color);     }    }   }   return destBmp;  }  #endregion  #region Public Methods  public Stream CreateCheckCodeImage()  {   string checkCode;   switch (_codetype)   {    case CodeType.Alphas:     checkCode = GenerateAlphas();     break;    case CodeType.Numbers:     checkCode = GenerateNumbers();     break;    case CodeType.Characters:     checkCode = GenerateCharacters();     break;    default:     checkCode = GenerateAlphas();     break;   }   this._checkCode = checkCode;   MemoryStream ms = null;   //   if (checkCode == null || checkCode.Trim() == String.Empty)    return null;   Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * _jianju)), (int)_height);   Graphics g = Graphics.FromImage(image);   try   {    Random random = new Random();    g.Clear(Color.White);    // 畫圖片的背景噪音線    for (int i = 0; i < 18; 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.FromArgb(random.Next()), 1), x1, y1, x2, y2);    }    Font font = new System.Drawing.Font("Times New Roman", 14, System.Drawing.FontStyle.Bold);    LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);    if (_codetype != CodeType.Words)    {     for (int i = 0; i < checkCode.Length; i++)     {      g.DrawString(checkCode.Substring(i, 1), font, brush, 2 + i * _jianju, 1);     }    }    else    {     g.DrawString(checkCode, font, brush, 2, 2);    }    // 畫圖片的前景噪音點    for (int i = 0; i < 150; i++)    {     int x = random.Next(image.Width);     int y = random.Next(image.Height);     image.SetPixel(x, y, Color.FromArgb(random.Next()));    }    // 畫圖片的波形濾鏡效果    if (_codetype != CodeType.Words)    {     image = TwistImage(image, true, 3, 1);    }    // 畫圖片的邊框線    g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);    ms = new System.IO.MemoryStream();    image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);   }   finally   {    g.Dispose();    image.Dispose();   }   return ms;  }  #endregion}

//參數一：產生幾個字符的驗證碼圖片 參數二：驗證碼的形式(數字、字母、數字字母混合都有)ValidCode validCode = new ValidCode(5, ValidCode.CodeType.Alphas);this.pictureBox2.Image = Bitmap.FromStream(validCode.CreateCheckCodeImage());