根据子对象字段值获取父对象

Question

I need to return all objects that have child objects with a certain field != null.

NOTE: EpicStoryId is nullable int (as in 'int?')

I have tried:

return _context.Features
            .Where(x => x.UserStories.Any(us => us.EpicStoryId.HasValue) 
                && x.Id == Id)
            .FirstOrDefault();

and I have tried:

return _context.Features
            .Where(x => x.UserStories.Any(us => us.EpicStoryId != null) 
                && x.Id == Id)
            .FirstOrDefault();

and for good measure:

return _context.Features
            .Where(x => x.UserStories.Any(us => us.EpicStoryId.HasValue == false) 
                && x.Id == Id)
            .FirstOrDefault();

and finally:

return _context.Features
            .Where(x => x.UserStories.Any(us => us.EpicStoryId > 0) 
                && x.Id == Id)
            .FirstOrDefault();

But none of these work. It's still returning every 'Feature' with Id=Id regardless if a child has a value for EpicStoryId or not. (FYI, I checked the data and there ARE null values for some EpicStoryId 's.)

sample data:

Answer 1

Any will return true i any 1 EpicStoryId has value so your your condition is failing.

All should do:-

return _context.Features
               .FirstOrDefault(x => x.UserStories.All(us => us.EpicStoryId.HasValue) 
                    && x.Id == Id);

Answer 2

If you need to return all objects then don't use FirstOrDefault() , use combination of .Where() and .ToList() methods :

For any of us EpicStoryIds are not null use :

return _context.Features
            .Where(x => x.Id == Id && x.UserStories.Any(us => us.EpicStoryId.HasValue))
            .ToList();

For all of us EpicStoryIds are not null you can use :

return _context.Features
            .Where(x => x.Id == Id && x.UserStories.All(us => us.EpicStoryId.HasValue))
            .ToList();

If you want to return list of UserStories and not Features , you can use :

return _context.Features
            .Where(x => x.Id == Id)
            .SelectMany(x => x.UserStories
              .Where(us => us.EpicStoryId.HasValue))
            .ToList();