左连接linq并获取右表中具有空值的行

Question

我有这个sql statemenet，现在想把这个sql改成linq c＃

Declare @PageMenuId int 
set @PageMenuId=131 
select * from MenuMaster as M
left join DynamicPages as P ON M.MenuId=P.PageMenuID 
where  P.Id is null or P.PageMenuID =@PageMenuId

我试过这个但是现在它不适合我。

MenuMaster objMenuMaster = new MenuMaster();
            DynamicPageManager objDynamicPage = new DynamicPageManager();
            IList<MenuMaster> lstMenuMaster = new List<MenuMaster>();
            IList<DynamicPage> lstDynamicPage = new List<DynamicPage>();
            IList<MenuMaster> resultMenuMaster = new List<MenuMaster>();
            try
            {

                lstMenuMaster = GetAll().ToList();
                lstDynamicPage = objDynamicPage.GetAll().ToList();


                 resultMenuMaster = from m in lstMenuMaster
                            join p in lstDynamicPage on m.MenuId equals p.PageMenuID into gj
                        from subpet in gj.DefaultIfEmpty()
                            where (subpet.Id == null) || (subpet.PageMenuID == PageId)
                                    select new MenuMaster  {



                                    };

            }
            catch (Exception ex)
            {
                _ErrorLog.CreateErrorLog(ex.Message, ex);

            }
            return resultMenuMaster;