lambda表达式查询两个时间之差的小时数

``` if (query.IsTime == true){

            linq = linq.Where(sl => sl.EndTime == null || (new TimeSpan(sl.EndTime.Ticks)).Subtract(new TimeSpan(DateTime.Now.Ticks)).Minutes <= 20);
}else {
           linq = linq.Where(s => (new TimeSpan(s.EndTime.Ticks)).Subtract(new TimeSpan(DateTime.Now.Ticks)).Minutes > 20);
      }

linq = linq.Where(x => x.EndTime > DateTime.Now.AddMinutes(20))