asp.net验证码生成类(参考)

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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>
 /// 生成验证码的类
 /// </summary>
 public class validatenumber
 {
  public validatenumber()
  {
  }
  /// <summary>
  /// 验证码的最大长度
  /// </summary>
  public int maxlength
  {
   get{return 10;}
  }
  /// <summary>
  /// 验证码的最小长度
  /// </summary>
  public int minlength
  {
   get{return 1;}
  }
  /// <summary>
  /// 生成验证码
  /// </summary>
  /// <param name="length">指定验证码的长度</param>
  /// <returns></returns>
  public string createvalidatenumber(int length)
  {
   int[] randmembers=new int[length];
   int[] validatenums=new int[length];
   string validatenumberstr="";
   //生成起始序列值
   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;
   }
   //生成随机数字
   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);
   }
   //抽取随机数字
   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));
   }
   //生成验证码
   for(int i=0;i<length;i++)
   {
    validatenumberstr+=validatenums[i].tostring();
   }
   return validatenumberstr;
  }
  /// <summary>
  /// 创建验证码的图片
  /// </summary>
  /// <param name="containspage">要输出到的page对象</param>
  /// <param name="validatenum">验证码</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
   {
    //生成随机生成器
    random random=new random();
    //清空图片背景色
    g.clear(color.white);
    //画图片的干扰线
    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);
    //画图片的前景干扰点
    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);
    //保存图片数据
    memorystream stream=new memorystream();
    image.save(stream,imageformat.jpeg);
    //输出图片
    containspage.response.clear();
    containspage.response.contenttype="image/jpeg";
    containspage.response.binarywrite(stream.toarray());
   }
   finally
   {
    g.dispose();
    image.dispose();
   }
  }
  /// <summary>
  /// 得到验证码图片的长度
  /// </summary>
  /// <param name="validatenumlength">验证码的长度</param>
  /// <returns></returns>
  public static int getimagewidth(int validatenumlength)
  {
   return (int)(validatenumlength*12.5);
  }
  /// <summary>
  /// 得到验证码的高度
  /// </summary>
  /// <returns></returns>
  public static double getimageheight()
  {
   return 22.5;
  }
 }
}

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