在一般处理程序里写一个简单验证码

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<%@ WebHandler Language="C#"
Class="验证码"
%>

using
System;

using
System.Web;

using
System.Drawing;

public
class 验证码 : IHttpHandler

{

    public
void ProcessRequest(HttpContext context)

    {

        context.Response.ContentType = "image/jpeg";

        string
code = GetCode();//获得随机数

        using
(Image img = GetImg(code))

        {

            img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);

        }

    }

    private
Image GetImg(string
code)

    {

        Bitmap bit = new
Bitmap(90, 35);

        using
(Graphics g = Graphics.FromImage(bit))

        {

            g.FillRectangle(Brushes.Brown, 0, 0, bit.Width, bit.Height);

            g.FillRectangle(Brushes.White, 1, 1, bit.Width - 2, bit.Height - 2);

            g.DrawString(code, new
Font("微软雅黑", 20), Brushes.Sienna, 3, 1);

        }

        return
bit;

    }

    //生成四位验证码

    private
string GetCode()

    {

        string
code = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        string
str = "";

        Random r = new
Random();

        for
(int
i = 0; i < 4; i++)

        {

            int
index = r.Next(0, code.Length);

            str += code[index];

        }

        return
str;

    }

    public
bool IsReusable

    {

        get

        {

            return
false;

        }

    }

}