asp.net驗證碼產生類(參考)

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using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Web.UI;
using System.Drawing.Drawing2D;
using System.IO;
namespace Validate
{
 /// <summary>
 /// 產生驗證碼的類
 /// </summary>
 public class ValidateNumber
 {
  public ValidateNumber()
  {
  }
  /// <summary>
  /// 驗證碼的最大長度
  /// </summary>
  public int MaxLength
  {
   get{return 10;}
  }
  /// <summary>
  /// 驗證碼的最小長度
  /// </summary>
  public int MinLength
  {
   get{return 1;}
  }
  /// <summary>
  /// 產生驗證碼
  /// </summary>
  /// <param name="length">指定驗證碼的長度</param>
  /// <returns></returns>
  public string CreateValidateNumber(int length)
  {
   int[] randMembers=new int[length];
   int[] validateNums=new int[length];
   string validateNumberStr="";
   //產生起始序列值
   int seekSeek=unchecked((int)DateTime.Now.Ticks);
   Random seekRand=new Random(seekSeek);
   int beginSeek=(int)seekRand.Next(0,Int32.MaxValue-length*10000);
   int[] seeks=new int[length];
   for(int i=0;i<length;i++)
   {
    beginSeek+=10000;
    seeks[i]=beginSeek;
   }
   //產生隨機數字
   for(int i=0;i<length;i++)
   {
    Random rand=new Random(seeks[i]);
    int pownum=1*(int)Math.Pow(10,length);
    randMembers[i]=rand.Next(pownum,Int32.MaxValue);
   }
   //抽取隨機數字
   for(int i=0;i<length;i++)
   {
    string numStr=randMembers[i].ToString();
    int numLength=numStr.Length;
    Random rand=new Random();
    int numPosition=rand.Next(0,numLength-1);
    validateNums[i]=Int32.Parse(numStr.Substring(numPosition,1));
   }
   //產生驗證碼
   for(int i=0;i<length;i++)
   {
    validateNumberStr+=validateNums[i].ToString();
   }
   return validateNumberStr;
  }
  /// <summary>
  /// 建立驗證碼的圖片
  /// </summary>
  /// <param name="containsPage">要輸出到的page對象</param>
  /// <param name="validateNum">驗證碼</param>
  public void CreateValidateGraphic(Page containsPage,string validateNum)
  {
   Bitmap image=new Bitmap((int)Math.Ceiling(validateNum.Length*12.5),22);
   Graphics g=Graphics.FromImage(image);
   try
   {
    //產生隨機產生器
    Random random=new Random();
    //清空圖片背景色
    g.Clear(Color.White);
    //畫圖片的幹擾線
    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 Font("Arial",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(validateNum,font,brush,3,2);
    //畫圖片的前景幹擾點
    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);
    //儲存圖片資料
    MemoryStream stream=new MemoryStream();
    image.Save(stream,ImageFormat.Jpeg);
    //輸出圖片
    containsPage.Response.Clear();
    containsPage.Response.ContentType="image/jpeg";
    containsPage.Response.BinaryWrite(stream.ToArray());
   }
   finally
   {
    g.Dispose();
    image.Dispose();
   }
  }
  /// <summary>
  /// 得到驗證碼圖片的長度
  /// </summary>
  /// <param name="validateNumLength">驗證碼的長度</param>
  /// <returns></returns>
  public static int GetImageWidth(int validateNumLength)
  {
   return (int)(validateNumLength*12.5);
  }
  /// <summary>
  /// 得到驗證碼的高度
  /// </summary>
  /// <returns></returns>
  public static double GetImageHeight()
  {
   return 22.5;
  }
 }
}