public void ShowCode()
  {
   //对象实例化
   Validate GifValidate = new Validate();

   #region 对验证码进行设置(不进行设置时,将以默认值生成)
   //验证码位数，不小于4位
   GifValidate.ValidateCodeCount = 4;
   //验证码字体型号(默认13)
   GifValidate.ValidateCodeSize = 13;
   //验证码图片高度,高度越大,字符的上下偏移量就越明显
   GifValidate.ImageHeight = 23;
   //验证码字符及线条颜色(需要参考颜色类)
   GifValidate.DrawColor = System.Drawing.Color.BlueViolet;
   //验证码字体(需要填写服务器安装的字体)
   GifValidate.ValidateCodeFont = "Arial";
   //验证码字符是否消除锯齿
   GifValidate.FontTextRenderingHint = false;
   //定义验证码中所有的字符(","分离),似乎暂时不支持中文
   GifValidate.AllChar = "1,2,3,4,5,6,7,8,9,0,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";
   #endregion

   //输出图像(Session名称)
   GifValidate.OutPutValidate("GetCode");
  }

public class Validate
 {
  public string AllChar = "1,2,3,4,5,6,7,8,9,0,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";
  public Color DrawColor = Color.BlueViolet;
  public bool FontTextRenderingHint = false;
  public int ImageHeight = 0x17;
  private byte TrueValidateCodeCount = 4;
  protected string ValidateCode = "";
  public string ValidateCodeFont = "Arial";
  public float ValidateCodeSize = 13f;

  private void CreateImageBmp(out Bitmap ImageFrame)
  {
   char[] chArray = this.ValidateCode.ToCharArray(0, this.ValidateCodeCount);
   int width = (int) (((this.TrueValidateCodeCount * this.ValidateCodeSize) * 1.3) + 4.0);
   ImageFrame = new Bitmap(width, this.ImageHeight);
   Graphics graphics = Graphics.FromImage(ImageFrame);
   graphics.Clear(Color.White);
   Font font = new Font(this.ValidateCodeFont, this.ValidateCodeSize, FontStyle.Bold);
   Brush brush = new SolidBrush(this.DrawColor);
   int maxValue = (int) Math.Max((float) ((this.ImageHeight - this.ValidateCodeSize) - 3f), (float) 2f);
   Random random = new Random();
   for (int i = 0; i < this.TrueValidateCodeCount; i++)
   {
    int[] numArray = new int[] { (((int) (i * this.ValidateCodeSize)) + random.Next(1)) + 3, random.Next(maxValue) };
    Point point = new Point(numArray[0], numArray[1]);
    if (this.FontTextRenderingHint)
    {
     graphics.TextRenderingHint = TextRenderingHint.SingleBitPerPixel;
    }
    else
    {
     graphics.TextRenderingHint = TextRenderingHint.AntiAlias;
    }
    graphics.DrawString(chArray[i].ToString(), font, brush, (PointF) point);
   }
   graphics.Dispose();
  }

  private void CreateImageGif()
  {
   AnimatedGifEncoder encoder = new AnimatedGifEncoder();
   MemoryStream stream = new MemoryStream();
   encoder.Start();
   encoder.SetDelay(5);
   encoder.SetRepeat(0);
   for (int i = 0; i < 10; i++)
   {
    Bitmap bitmap;
    this.CreateImageBmp(out bitmap);
    this.DisposeImageBmp(ref bitmap);
    bitmap.Save(stream, ImageFormat.Png);
    encoder.AddFrame(Image.FromStream(stream));
    stream = new MemoryStream();
   }
   encoder.OutPut(ref stream);
   HttpContext.Current.Response.ClearContent();
   HttpContext.Current.Response.ContentType = "image/Gif";
   HttpContext.Current.Response.BinaryWrite(stream.ToArray());
   stream.Close();
   stream.Dispose();
  }

  private void CreateValidate()
  {
   this.ValidateCode = "";
   string[] strArray = this.AllChar.Split(new char[] { ',' });
   int index = -1;
   Random random = new Random();
   for (int i = 0; i < this.ValidateCodeCount; i++)
   {
    if (index != -1)
    {
     random = new Random((i * index) * ((int) DateTime.Now.Ticks));
    }
    int num3 = random.Next(0x23);
    if (index == num3)
    {
     this.CreateValidate();
    }
    index = num3;
    this.ValidateCode = this.ValidateCode + strArray[index];
   }
   if (this.ValidateCode.Length > this.TrueValidateCodeCount)
   {
    this.ValidateCode = this.ValidateCode.Remove(this.TrueValidateCodeCount);
   }
  }

  private void DisposeImageBmp(ref Bitmap ImageFrame)
  {
   Graphics graphics = Graphics.FromImage(ImageFrame);
   Pen pen = new Pen(this.DrawColor, 1f);
   Random random = new Random();
   Point[] pointArray = new Point[2];
   for (int i = 0; i < 15; i++)
   {
    pointArray[0] = new Point(random.Next(ImageFrame.Width), random.Next(ImageFrame.Height));
    pointArray[1] = new Point(random.Next(ImageFrame.Width), random.Next(ImageFrame.Height));
    graphics.DrawLine(pen, pointArray[0], pointArray[1]);
   }
   graphics.Dispose();
  }

  public void OutPutValidate(string ValidateCodeSession)
  {
   this.CreateValidate();
   this.CreateImageGif();
   HttpContext.Current.Session[ValidateCodeSession] = this.ValidateCode;
  }

  public byte ValidateCodeCount
  {
   get
   {
    return this.TrueValidateCodeCount;
   }
   set
   {
    if (value > 4)
    {
     this.TrueValidateCodeCount = value;
    }
   }
  }
 }