ASP.NET HttpModule实验

利用HttpModule实现图片验证码.无实用价值，仅实验HttpModule功能使用。

说明：图片生成部分抄自张子阳的Asp.Net架构

using System;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text;

namespace MyHttpModule {

    public class MyHttpModule :IHttpModule {
        public void Init(HttpApplication app) {
            app.BeginRequest += new EventHandler(this.App_BeginRequest);
            //app.EndRequest += new EventHandler(this.App_EndRequest);
            //app.PreRequestHandlerExecute += new EventHandler(this.App_PreRequest);
        }

        public void App_PreRequest(Object obj, EventArgs e) {
            HttpApplication app = (HttpApplication)obj;
            HttpContext ctx = app.Context;
            HttpResponse rsp = ctx.Response;
            
            rsp.Write(ctx.CurrentHandler.GetType().FullName);
            rsp.Write("<br/>");
            rsp.Write(ctx.CurrentHandler.ToString());
            rsp.Write("<br/>");
            rsp.Write(ctx.CurrentHandler.IsReusable);
            rsp.Write("<br/>");
            rsp.Write(ctx.CurrentHandler.GetHashCode());
            rsp.Write("<br/>");
            rsp.Write("-----华丽的分割线----------");
            rsp.Write("<br/>");
            rsp.Write(ctx.Handler.GetType().FullName);
            rsp.Write("<br/>");
            rsp.Write(ctx.Handler.ToString());
            rsp.Write("<br/>");
            rsp.Write(ctx.Handler.IsReusable);
            rsp.Write("<br/>");
            rsp.Write(ctx.CurrentHandler.GetHashCode());
            rsp.Write("<br/>");
            
            //ctx.CurrentHandler.ProcessRequest(ctx);
            //app.CompleteRequest();
        }

        public void App_BeginRequest(Object obj, EventArgs e) {
            HttpApplication app = (HttpApplication)obj;
            HttpContext ctx = app.Context;
            HttpResponse rsp = ctx.Response;
            //rsp.Write("我来自Application Begin Request");
            rsp.ContentType = "image/gif";
            Bitmap basemap = new Bitmap(200, 60);
            Graphics graph = Graphics.FromImage(basemap);
            graph.FillRectangle(new SolidBrush(Color.White), 0, 0, 200, 60);
            Font font = new Font(FontFamily.GenericSerif, 48, FontStyle.Bold, GraphicsUnit.Pixel);
            Random r = new Random();
            String letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            String letter;
            StringBuilder s = new StringBuilder();
            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 * 38, r.Next(0, 15));
            }

            Pen linePen = new Pen(new SolidBrush(Color.Black), 2);
            for (int x = 0; x < 6; x++) {
                graph.DrawLine(linePen, new Point(r.Next(0, 199), r.Next(0, 59)), new Point(r.Next(0, 199), r.Next(0, 59)));
            }

            basemap.Save(rsp.OutputStream, ImageFormat.Gif);
            rsp.End();
        }

        public void App_EndRequest(Object obj, EventArgs e) {
            HttpApplication app = (HttpApplication)obj;
            HttpContext ctx = app.Context;
            HttpResponse rsp = ctx.Response;
            rsp.Write("我来自Application End Request");
        }

        public void Dispose() {
        }
    }
}