两个关键的类是ModuleRewriter和RewriterFactoryHandler
  ModuleRewriter类用于Url重定向，代码如下：

ModuleRewriter
using System;
using System.Text.RegularExpressions;
using System.Configuration;
using URLRewriter.Config;
using System.Data;
using System.Web;
using System.Web.UI;
namespace URLRewriter
{
/**////

public class ModuleRewriter : BaseModuleRewriter
{
/**////

/// The RawUrl being requested (includes path and querystring). /// The HttpApplication instance. protected override void Rewrite(string requestedPath, System.Web.HttpApplication app)
{
//只对文件后缀为aspx页面有效
if (requestedPath.IndexOf(“.aspx”) != -1)
{
HttpContext httpContext = app.Context;

// get the configuration rules
RewriterRuleCollection rules = RewriterConfiguration.GetConfig().Rules;

// iterate through each rule
for (int i = 0; i < rules.Count; i++)
{
// get the pattern to look for, and Resolve the Url (convert ~ into the appropriate directory)
string lookFor = “^” + RewriterUtils.ResolveUrl(httpContext.Request.ApplicationPath, rules[i].LookFor) + “$”;

// Create a regex (note that IgnoreCase is set)
Regex re = new Regex(lookFor, RegexOptions.IgnoreCase);

// See if a match is found
if (re.IsMatch(requestedPath))
{
//aspx页面重定向到htm页面且http数据传输方式为“GET”
if (rules[i].Type == WebType.Static && app.Context.Request.RequestType == “GET”)
{
//静态页面路径
string htmlWeb = RewriterUtils.ResolveUrl(httpContext.Request.ApplicationPath, rules[i].SendTo);
//静态页面的最后修改时间
DateTime dt = System.IO.File.GetLastWriteTime(httpContext.Server.MapPath(htmlWeb));
//当前时间和静态页面生成时间对比，如果时间小于一个小时，重定向到静态页面
if (DateTime.Compare(DateTime.Now.AddHours(-1), dt) <= 0)
{
requestedPath = htmlWeb;
}
}
else
{
requestedPath = rules[i].SendTo;
}

// Rewrite the URL
RewriterUtils.RewriteUrl(httpContext, requestedPath);
break; // exit the for loop
}
}
}
}

}
}
CreateHtmFactoryHandler类用于生成静态页面，代码如下：
CreateHtmFactoryHandler
using System;
using System.IO;
using System.Web.UI;
using System.Web;
using URLRewriter.Config;
using System.Configuration;
using System.Text.RegularExpressions;

namespace URLRewriter
{
/**////

public class CreateHtmFactoryHandler : IHttpHandlerFactory
{
/**////

/// HttpContext 类的实例，它提供对用于为 HTTP 请求提供服务的内部服务器对象（如 Request、Response、Session 和 Server）的引用 /// 客户端使用的 HTTP 数据传输方法（GET 或 POST） /// 所请求资源的 RawUrl。 /// 所请求资源的 PhysicalApplicationPath /// 返回实现 IHttpHandler 接口的类的实例
public virtual IHttpHandler GetHandler(HttpContext context, string requestType, string url, string pathTranslated)
{
if (requestType == “GET”)
{
// get the configuration rules
RewriterRuleCollection rules = RewriterConfiguration.GetConfig().Rules;

// iterate through each rule
for (int i = 0; i < rules.Count; i++)
{
// get the pattern to look for, and Resolve the Url (convert ~ into the appropriate directory)
string lookFor = “^” + RewriterUtils.ResolveUrl(context.Request.ApplicationPath, rules[i].LookFor) + “$”;

// Create a regex (note that IgnoreCase is set)
Regex re = new Regex(lookFor, RegexOptions.IgnoreCase);

// See if a match is found
if (re.IsMatch(url) && rules[i].Type == WebType.Static)
{
//得到要生成的静态页面的物理路径
string physicsWeb = context.Server.MapPath(RewriterUtils.ResolveUrl(context.Request.ApplicationPath, rules[i].SendTo));
//设定Response筛选器
context.Response.Filter = new ResponseFilter(context.Response.Filter, physicsWeb);
break;
}
}
}
//得到编译实例
return PageParser.GetCompiledPageInstance(url, pathTranslated, context);
}

public virtual void ReleaseHandler(IHttpHandler handler)
{
}
}
}   以上是两个主要的类，还有一些辅助的类，我把测试项目附上，里边有源代码和示例。
  点击这里下载：源代码和示例
  声明一下，我是在修改一个开源的项目（UrlRewrite）来实现上述功能。有关UrlRewrite介绍，请看这里，ASP.NET 中执行 URL 重写。