IQueryable 查询中的求和时间跨度

Question

I can not sum time of episodes until I convert query to IEnumerable

this my code

IQueryable<Course> result = db.Courses;
GetCoursesViewModel list = new GetCoursesViewModel();
list.Courses = await result
            .Skip(skip)
            .Take(getCourses.Take)
            .Select(c => new GetCoursesListViewModel
            {
                Id = c.CourseId,
                Title = c.CourseTitle,
                Price = c.CoursePrice,
                Group = c.CourseGroup.GroupTitle,
                Level = c.CourseLevel.LevelTitle,
                Status = c.CourseStatus.StatusTitle,
                ImageName = c.CourseImageName,
                EpisodeCount = c.CourseEpisodes.Count,
                ShortDescription = c.CourseShortDescription,
                /*TotalTime = new TimeSpan(c.CourseEpisodes.Sum(e => e.EpisodeTime.Ticks)),*/ could not be translated.
                Teacher = c.User.UserName
            }).ToListAsync();

Is there a way I can get the total duration using IQueryable?