Code
private static object _SyncRoot = new object();
        private static List<Post> _Posts;
        /// <summary>
        /// A sorted collection of all posts in the blog.
        /// Sorted by date.
        /// </summary>
        public static List<Post> Posts
        {
            get
            {
                if (_Posts == null)
                {
                    lock (_SyncRoot)
                    {
                        if (_Posts == null)
                        {
                            _Posts = BlogService.FillPosts();
                            //记录首次加载时间
                            using (FileStream f = new FileStream(HttpContext.Current.Server.MapPath(Utils.RelativeWebRoot+@"/app_data/firstLoadPosts.txt"), FileMode.Append, FileAccess.Write))
                            {

                                StreamWriter s = new StreamWriter(f);
                                s.WriteLine(DateTime.Now.ToString());
                                s.Flush();
                                s.Close();
                            }
                            //记录结束
                            _Posts.TrimExcess();
                            AddRelations();
                        }
                    }
                }

                return _Posts;
            }
        }