缓存XML文件方法的实现

        private static PageInfo GetPageInfoByUrlInXml(string url)
        {
            Hashtable hs =new Hashtable();
            PageInfo pi=null;
            if (HttpContext.Current.Cache["PageInfo"]!=null)
            {
                hs = (Hashtable) HttpContext.Current.Cache["PageInfo"];
                if (hs == null)
                {
                    hs = SiteCommon.XMLFunction.GetPageInfoByXML();
                    HttpContext.Current.Cache.Remove("PageInfo");
                    HttpContext.Current.Cache.Insert("PageInfo",hs,null,  
                                                     System.Web.Caching.Cache.NoAbsoluteExpiration,  
                                                     TimeSpan.FromDays(30));
                }
            }
            else
            {
                hs = SiteCommon.XMLFunction.GetPageInfoByXML();
                HttpContext.Current.Cache.Insert("PageInfo", hs,null,System.Web.Caching.Cache.NoAbsoluteExpiration,
                                                  TimeSpan.FromDays(30));
            }
            
            foreach(System.Collections.DictionaryEntry de in hs)
            {
                if (url.IndexOf(de.Key.ToString().ToLower()) != -1 && url.ToLower().Trim()!="/index.aspx") return (PageInfo) hs[de.Key.ToString()];
            }
            
            return pi;
        }