asp.net配置全局应用程序类 巧妙达到定时生成静态页面

//在项目里添加一个"全局应用程序类(Global Application Class)",在里面写这样的代码：
public class Global : System.Web.HttpApplication
{
    static Timer BuildStaticPagesTimer;
    static object locker = new object();
    static int count;

    protected void Application_Start(object sender, EventArgs e)
    {
        //double check lock...
        if (BuildStaticPagesTimer == null)
        {
            lock (locker)
            {
                if (BuildStaticPagesTimer == null)
                {
                    //every 20 minutes, run BuildStaticPagesTimer_Callback in every 20 minutes
                    BuildStaticPagesTimer = new Timer(BuildStaticPagesTimer_Callback, null, 0, 20 * 60 * 1000);
                }
            }
        }
    }

    private static void BuildStaticPagesTimer_Callback(object state)
    {
        Dictionary<string, string> urlsNeedToBuild = GetPagesNeedToBuiltStatic();
        foreach (string oldUrl in urlsNeedToBuild.Keys)
        {
            string newUrl = urlsNeedToBuild[oldUrl];
            Build(oldUrl, newUrl);
        }
    }

    private static void Build(string oldUrl, string newUrl)
    {
        //在这里写生成静态页面的代码
        throw new NotImplementedException();
    }

    private static Dictionary<string, string> GetPagesNeedToBuiltStatic()
    {
        //在这里判断哪些页面需要生成静态页面
        throw new NotImplementedException();
    }
}