ASP.NET实现的生成验证码功能示例【附demo源码】

本文实例讲述了asp.net实现的生成验证码功能。分享给大家供大家参考，具体如下：

生成验证码原理：产生随机字符，并将字符生成为图片，同时储存到session里去，然后验证用户输入的内容是否与session中的验证码相符即可。

效果图：用户可以点击切换验证码信息。

一般处理程序：checkcodehandler.cs

<%@ webhandler language="c#" class="checkcodehandler" %>
using system;
using system.web;
using system.text;
using system.drawing;
using system.web.sessionstate;
public class checkcodehandler : ihttphandler,irequiressessionstate
{
  //产生验证码的字符集
  public string charcode = "2,3,4,5,6,8,9,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y";
  public void processrequest (httpcontext context) {
    string validatecode = createrandomcode(4);
    context.session["validatecode"] = validatecode;//将验证码保存到session中
    createcodeimage(validatecode, context);
  }
  public bool isreusable {
    get {
      return false;
    }
  }
  /// <summary>
  /// 生成验证码
  /// </summary>
  /// <param name="n">验证码个数</param>
  /// <returns>验证码字符串</returns>
  public string createrandomcode(int n)
  {
    string[] chararray = charcode.split(',');//将字符串转换为字符数组
    string randomcode = "";
    int temp = -1;
    random rand = new random();
    for (int i = 0; i < n; i++)
    {
      if (temp != -1)
      {
        rand = new random(i * temp * ((int)datetime.now.ticks));
      }
      int t = rand.next(chararray.length - 1);
      if (temp != -1 && temp == t)
      {
        return createrandomcode(n);
      }
      temp = t;
      randomcode += chararray[t];
    }
    return randomcode;
  }
  public void createcodeimage(string checkcode, httpcontext context)
  {
    int iwidth = (int)(checkcode.length * 13);
    system.drawing.bitmap image = new system.drawing.bitmap(iwidth, 20);
    graphics g = graphics.fromimage(image);
    font f = new system.drawing.font("arial", 12, (system.drawing.fontstyle.italic | system.drawing.fontstyle.bold));
    // 前景色
    brush b = new system.drawing.solidbrush(color.black);
    // 背景色
    g.clear(color.white);
    // 填充文字
    g.drawstring(checkcode, f, b, 0, 1);
    // 随机线条
    pen linepen = new pen(color.gray, 0);
    random rand = new random();
    for (int i = 0; i < 5; i++)
    {
      int x1 = rand.next(image.width);
      int y1 = rand.next(image.height);
      int x2 = rand.next(image.width);
      int y2 = rand.next(image.height);
      g.drawline(linepen, x1, y1, x2, y2);
    }
    // 随机点
    for (int i = 0; i < 30; i++)
    {
      int x = rand.next(image.width);
      int y = rand.next(image.height);
      image.setpixel(x, y, color.gray);
    }
    // 边框
    g.drawrectangle(new pen(color.gray), 0, 0, image.width - 1, image.height - 1);
    // 输出图片
    system.io.memorystream ms = new system.io.memorystream();
    image.save(ms, system.drawing.imaging.imageformat.jpeg);
    context.response.clearcontent();
    context.response.contenttype = "image/jpeg";
    context.response.binarywrite(ms.toarray());
    g.dispose();
    image.dispose();
  }
}

封装成类库：validatenumber.cs

using system;
using system.collections.generic;
using system.linq;
using system.web;
using system.drawing;
using system.web.ui;
using system.drawing.drawing2d;
using system.io;
using system.drawing.imaging;
/// <summary>
///validatenumber 生成验证码
/// </summary>
public class validatenumber
{
  //产生验证码的字符集 （易混淆的字符去掉）
  private string charcode = "2,3,4,5,6,8,9,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y";
  /// <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)
  {
    string[] chararray = charcode.split(',');//将字符串转换为字符数组
    string randomcode = "";
    int temp = -1;
    random rand = new random();
    for (int i = 0; i < length; i++)
    {
      if (temp != -1)
      {
        rand = new random(i * temp * ((int)datetime.now.ticks));
      }
      int t = rand.next(chararray.length - 1);
      if (temp != -1 && temp == t)
      {
        return createvalidatenumber(length);
      }
      temp = t;
      randomcode += chararray[t];
    }
    return randomcode;
  }
  /// <summary>
  /// 创建验证码的图片
  /// </summary>
  /// <param name="context">context对象</param>
  /// <param name="validatenum">验证码</param>
  public void createvalidategraphic(httpcontext context,string validatenum)
  {
    int iwidth = (int)(validatenum.length * 14);
    bitmap image = new bitmap(iwidth, 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
      context.response.clear();
      context.response.contenttype = "image/jpeg";
      context.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 * 14);
  }
  /// <summary>
  /// 得到验证码图片的高度
  /// </summary>
  /// <returns></returns>
  public static double getimageheight()
  {
    return 22;
  }
}

附：完整实例代码点击此处。

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