Question

我为嵌套在顶层实体中的实体集合获取空值。如何正确编写LINQ查询以使这些值不为空？

我正在使用Entity Framework 7和MVC 6以下是我的课程：

我的模特：

public class WorkStation
{
    public Id { get; set; }
    public string Name{ get; set; }
    public ICollection<PersonWorkStation> PersonWorkStations{ get; set; }
}

public class Person
{
    public Id { get; set; }
    public string FirstName { get; set; }
    public ICollection<PersonWorkStation> PersonWorkStations{ get; set; }
}

public class PersonWorkStation
{
    public int Id { get; set; }

    public int PersonId { get; set; }
    public Person Person { get; set; }

    public int WorkStationId { get; set; }
    public WorkStation WorkStation { get; set; }
}

我的DbContext：

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<PersonWorkStation>()
            .HasKey(op => new { op.Id });

        modelBuilder.Entity<PersonWorkStation>()
            .HasOne(pt => pt.Person)
            .WithMany(p => p.PersonWorkStation)
            .HasForeignKey(pt => pt.PersonId);

        modelBuilder.Entity<PersonWorkStation>()
            .HasOne(pt => pt.WorkStation)
            .WithMany(t => t.PersonWorkStation)
            .HasForeignKey(pt => pt.WorkStationId);

        base.OnModelCreating(modelBuilder);
    }

所以说到这一点，当我带回一个人，并查看＆＃34; PersonWorkStation＆＃34;集合时，WorkStation属性为null。我怎样才能把这个实体带回来？

以下是我检索数据的方法：

        var person = _context.Persons
            .Include(p => p.PersonWorkStation)
            .FirstOrDefault(p => p.Id == 1);

        return person;

同样，对于person.PersonWorkStations集合中的所有项，person.PersonWorkStations.Workstation实体为null。我该如何归还这个实体？

谢谢！

Answer 1

我找到了答案，我需要添加这一行：

var person = _context.Persons
        .Include(p => p.PersonWorkStation)
        .ThenInclude(p => p.WorkStation)
        .FirstOrDefault(p => p.Id == 1);

return person;

EF7为实体的多个实体集合获取空值

1 个答案: