/// 
/// 生成验证码图片/// 
public void CreateCheckCodeImage(){string checkCode = VerficationCodeSrc(5);if (checkCode == null || checkCode.Trim() == String.Empty)return;//string checkCode = "asfd2";Bitmap image = new Bitmap(90, 28);Graphics g = Graphics.FromImage(image);try{//生成随机生成器 Random random = new Random();//清空图片背景色 g.Clear(Color.White);//画图片的背景噪音线 for (int i = 0; i < 2; 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.Black), x1, y1, x2, y2);}Font font = new Font("Arial", 16, (FontStyle.Bold));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);//画图片的前景噪音点 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()));}//画图片的边框线 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();}}/// 
/// 生成验证码字符串/// 
/// /// 
     private string VerficationCodeSrc(int numberOfChars){if (numberOfChars > 36){throw new InvalidOperationException("Random Word Charecters can not be greater than 36.");}char[] columns = new char[36];//字母for (int charPos = 97; charPos < 97 + 26; charPos++)columns[charPos - 97] = (char)charPos;//数字for (int intPos = 48; intPos <= 57; intPos++)columns[intPos - 22] = (char)intPos;StringBuilder randomBuilder = new StringBuilder();Random randomSeed = new Random();for (int incr = 0; incr < numberOfChars; incr++){randomBuilder.Append(columns[randomSeed.Next(36)].ToString());}return randomBuilder.ToString();}