实体框架 - 根据外键添加对象

Question

I'm working on a semi-enterprise WPF Application, using EF6+ (any version is okay, I can update it any time I like).

I already have the database set-up (from previous project, it's a MSSQL db), and I'm doing code first obviously. I'll use mock objects due to NDA.

I would like to know what to do in order for EF to inject Son object from the database into the Man object as marked by Foreign Key. eg:

[Table("Man")]
public class Man : ObservableObject
{
    private int _id;

    private int _sonId;
    private Son _son;

    public int Id
    {
        get => _id;
        set => Set(() => Id, ref _id, value);
    }

    [ForeignKey("SonId")]
    public Son Son
    {
        get => _son;
        set => Set(() => Son, ref _son, value);
    }

    public int SonId
    {
        get => _sonId;
        set => Set(() => SonId, ref _sonId, value);
    }
}

[Table("Son")]
public class Son : ObservableObject
{
    private int _id;

    public int Id
    {
        get => _id;
        set => Set(() => Id, ref _id, value);
    }
}

I properly retrieve (using their respective repositories) objects from the database, however the Foreign Key object ( Son ) is not mapped (it's null). Is this not an option in EF or I'm doing something wrong?

Repository

public async Task<IEnumerable<Man>> GetAll()
{
    using (var ctx = new DatabaseContext())
    {
        return await ctx.Men.ToListAsync();
    }
}

I did not use any [Key] annotation, because I assume EF associates Id field as a primary key since my table PK is Id , and I have some validation in other classes like [StringLength] and [Range(1,10)] , etc... Which I assume is not relevant for this problem.

Answer 1

With EF6 you can use Include to eager load your child objects. I am not aware of a way to load multiple children without chaining Includes. You could create an extension method for loading all the children as shown here . Also note there are some changes with EF Core .

BTW, your class could be simplified if you are not altering the backing fields:

public class Man : ObservableObject  // ToTable Man by default
{
    public int Id { get; set; } //PK by convention

    public int SonId { get; set; } // FK by convention
    public Son Son { get; set; } 
}