实体框架一对多问题

Question

I use Entity Framework in my project. I stuck in some trouble.

I have two classes. Here are they:

public class User
{
    public virtual Guid Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public virtual string Username { get; set; }
    public string Email { get; set; }
    public virtual Company Company { get; set; }
}

public class Company
{
    public Guid Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public string Requisites { get; set; }
    public virtual List<User> Workers { get; set; }
}

Also I have repo. So when I create a new user and I want to add this user to company. How should I implement that? I have two ways:

1. user.Company = company;
2. company.Workers.Add(user);

Which way is preferable?

Answer 1

If company is already attached to the context.

Either

var company = db.Set<Company>().Find(companyId);

or

db.Set<Company>().Attach(company);

user.Company = company;

In the first case, if you only do that. The user will not be added to the database, you need to have this too.

db.Entry(user).State = EntityState.Added;

or

db.Set<User>().Add(user);

Then user will be added and will have relationship with company.

company.Workers.Add(user);

This one only should be okay, the user will be added and have relationship with company. But be careful if Workers is null, you need to instantiate it first.