HttpHandler 创建图片验证码

1 打开Vs2005，“添加新项”，“一般处理程序”。新建文件后，VS会自动在文件中添加如下的代码：

2:创建以下程序
<%@ WebHandler Language="C#" Class="Handler" %>

using System;
using System.Web;
using System.Drawing.Imaging;
using System.Drawing;
using System.Text;
public class Handler : IHttpHandler, System.Web.SessionState.IRequiresSessionState
{
   
    public void ProcessRequest (HttpContext context)
    {
        context.Request.ContentType="image/gif";
        Bitmap bitmap = new Bitmap(100, 30);
        Graphics graphic = Graphics.FromImage(bitmap);
        graphic.FillRectangle(new SolidBrush(Color.White), 0, 0, 100, 30);
        Font font = new Font(FontFamily.GenericSansSerif, 24, FontStyle.Bold, GraphicsUnit.Pixel);
        Random random = new Random();
        string letters = "ABCDEFGHIJKLMNPQRSTUVWXYZ";
        string letter;
        StringBuilder s = new StringBuilder();

        for (int i = 0; i < 5; i++)
        {
            letter = letters.Substring(random.Next(0,letters.Length-1), 1);
            s.Append(letters);
            graphic.DrawString(letter, font, new SolidBrush(Color.Red), i * 19, random.Next(0, 15));
        }
        float penFloat = new float();
        penFloat = float.Parse("0.5"); ;
        Pen linePen = new Pen(new SolidBrush(Color.Purple), penFloat);
        for (int x = 0; x < 20; x++)
            graphic.DrawLine(linePen, new Point(random.Next(0, 199), random.Next(0, 59)), new Point(random.Next(0, 199), random.Next(0, 59)));

       
        bitmap.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;
        }
    }

}
3:创建页面 ,添加Img

<img src="Handler.ashx" alt="图片验证码" />

<img src="Handler.ashx" alt="图片验证码" />