asp.net简单生成验证码的方法_.net

asp.net简单生成验证码的方法

本文实例讲述了asp.net简单生成验证码的方法。分享给大家供大家参考，具体如下：

1.新建一个一般处理程序

namespace webapplication1
{
 /// <summary>
 /// $codebehindclassname$ 的摘要说明
 /// </summary>
 [webservice(namespace = "http://tempuri.org/")]
 [webservicebinding(conformsto = wsiprofiles.basicprofile1_1)]
 public class handler1 : ihttphandler, irequiressessionstate
 {
  public void processrequest(httpcontext context)
  {
   context.response.contenttype = "image/gif";
   //建立bitmap对象，绘图
   bitmap basemap = new bitmap(100, 30);
   graphics graph = graphics.fromimage(basemap);
   graph.fillrectangle(new solidbrush(color.white), 0, 0, 100, 30);
   font font = new font(fontfamily.genericserif, 24, fontstyle.bold, graphicsunit.pixel);
   random r = new random();
   string letters = "abcdefghijklmnpqrstuvwxyz";
   string letter;
   stringbuilder s = new stringbuilder();
   //添加随机的五个字母
   for (int x = 0; x < 5; x++)
   {
    letter = letters.substring(r.next(0, letters.length - 1), 1);
    s.append(letter);
    graph.drawstring(letter, font, new solidbrush(color.black), x * 19, r.next(0, 8));
   }
   //混淆背景
   pen linepen = new pen(new solidbrush(color.black), 2);
   for (int x = 0; x < 6; x++)
    graph.drawline(linepen, new point(r.next(0, 99), r.next(0, 29)), new point(r.next(0, 99), r.next(0, 29)));
   //将图片保存到输出流中  
   basemap.save(context.response.outputstream, imageformat.gif);
   context.session["checkcode"] = s.tostring(); //如果没有实现irequiressessionstate，则这里会出错，也无法生成图片
   context.response.end();
  }
  public bool isreusable
  {
   get
   {
    return false;
   }
  }
 }
}

2.前台代码

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
 <title></title>
</head>
<body>
 <form id="form1" runat="server">
 <div>
  <asp:textbox id="txtcode" runat="server"></asp:textbox>
  <img id="imgcode" alt="看不清？点击换一张" src="handler1.ashx" style="cursor:pointer" onclick="this.src=this.src+'?'" /><br />
  <asp:button id="button1" runat="server" onclick="button1_click" text="button" />
 </div>
 </form>
</body>
</html>

希望本文所述对大家asp.net程序设计有所帮助。