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
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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;
}
}
}
}
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2.前台代码
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<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>
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希望本文所述对大家asp.net程序设计有所帮助。