static void Main()
        {
            DataClasses1DataContext db = new DataClasses1DataContext();
            string filePath = Environment.CurrentDirectory + @"\linq5.txt";
            System.IO.TextWriter log = System.IO.File.CreateText(filePath);
            //指定该datacontext的log文件路径，用以记录查询过程中的sql语句log
            db.Log = log;
            //制定log输出路径为控制台输出
            //db.Log = Console.Out;
            var obj = from m in db.test select new { m.ID, m.name };
            obj.ToList();//必须是sql执行后才能记入log文件中
            log.Close();