LINQ 表达式过滤

Question

I have the following LINQ expression where I am fetching Courses , Students that belong to that Course , then the School 's where the Student 's goes to. The following LINQ expression works fine.

However, I need to further, filter it where I need to get Students with the City == 'Colarado' . How can I alter the following LINQ to my use case.

     _dbContext.Courses
         .Where(c => c.Id == Id)
         .Include(c => c.Students)
             .ThenInclude(c => c.Schools)
         .OrderByDescending(c => c.Id)
         .ToListAsync();

Answer 1

If you need all courses and only filter students - since EF Core 5.0 you can use filtered include :

 _dbContext.Courses
     .Where(c => c.Id == Id)
     .Include(c => c.Students.Where(s => s.City == "Colarado"))
         .ThenInclude(c => c.Schools)
     .OrderByDescending(c => c.Id)
     .ToListAsync(); 

Answer 2

You can do the filter in the Where method.

_dbContext.Courses
     .Where(c => c.Id == Id && c.Students.All(s => s.City == "Colarado"))
     .Include(c => c.Students)
         .ThenInclude(c => c.Schools)
     .OrderByDescending(c => c.Id)
     .ToListAsync();