EF6代码优先多对多（无集合）

Question

So I have the following model in EF:

public class User: IEntity
{
    public Guid Id { get; protected set; }
    public string Email { get; protected set; }
    internal User()
    {
    }

    public User(Guid id, string email)
    {
        Id = id;
        Email = email;
    }
}

public class Tenant : IEntity
{
    public Guid Id { get; protected set; }
    public string Name { get; protected set; }

    internal Tenant() { }

    public Tenant(Guid id, string name)
    {
        Id = id;
        Name = name;
    }
}

I would like to have a many-to-many relationship between these entities without having collections in them.

I have tried creating a join entity like:

public class TenantUser
{
    public int Id { get; set; }
    public virtual Tenant Tenant { get; set; }
    public virtual User User { get; set; }

    internal TenantUser ()
    {
    }

    public TenantUser(Tenant tenant, User user )
    {
        this.Tenant = tenant;
        this.User = user;
    }
}

With the following setup:

modelBuilder.Entity<TenantUser>()
   .HasRequired<Tenant>(m => m.Tenant)
   .WithMany();

modelBuilder.Entity<TenantUser>()
   .HasRequired<User>(m => m.User)
   .WithMany();

When I save TenantUser objects, the database is populated with the correct foreign keys. When I query the TenantUser DbSet for all rows, it returns all rows, but I'm only getting the Id value populated, Tenant and User are both null.

I tried adding TenantId and UserId fields to TenantUser and then doing HasForeignKey for those fields, but it made no difference; TenantId and UserId were populated on query, but Tenant and User were still null.

I feel like I'm missing something simple here. Any thoughts would be great :)

Answer 1

If you want many-to-many then remove the configuration:

modelBuilder.Entity<TenantUser>()
.HasRequired<Tenant>(m => m.Tenant)
.WithMany();

modelBuilder.Entity<TenantUser>()
.HasRequired<User>(m => m.User)
.WithMany();

Why? Because EF use agreements:

public class User: IEntity
{
    public Guid Id { get; protected set; }
}

public class Tenant : IEntity
{
    public Guid Id { get; protected set; }
}

public class TenantUser
{
    public int Id { get; set; }
    public virtual Tenant Tenant { get; set; }
    public virtual User User { get; set; }
}

This is fluent many-to-many.

When you make a query, use:

public class UnitOfWork : DbContext
{
    public IDbSet<User> Users { get; set; }
    public IDbSet<Tenant> Tenants { get; set; }
    public IDbSet<TenantUser> TenantUsers { get; set; }
}

context.TenantUsers.Include(e => e.Tenant).Include(e => e.User);

Then EF Include them in the mapping