Entity Framework 4 (Linq query doesn't return my roles)

Question

I am currently working on my own version of membership using Entity Framework 4.0 and POCO.

After readying Scotts Gu blog post I decided to use conventions as much as possible.

So far I have a class called User:

public class User
{
    [System.ComponentModel.DataAnnotations.Key]
    public int UserId { get; set; }

    [System.ComponentModel.DataAnnotations.StringLength(60)] 
    public string UserName { get; set; }

    public string Password { get; set; }

    [System.ComponentModel.DataAnnotations.ConcurrencyCheck]
    public string Email { get; set; }

    [System.ComponentModel.DataAnnotations.Timestamp]
    public byte[] Timestamp { get; set; }

    public ICollection<Role> Roles { get; set; }
}

and a class called Role

public class Role
{
    [System.ComponentModel.DataAnnotations.Key]
    public int RoleId { get; set; }

    [System.ComponentModel.DataAnnotations.StringLength(50)]
    public string RoleName { get; set; }

    [System.ComponentModel.DataAnnotations.StringLength(300)]
    public string RoleDescription { get; set; }

    public ICollection<User> Users { get; set; }
}

I also implement DbContext like this :

public class BackboneDbContext : DbContext
{
    public DbSet<User> Users { get; set; }
    public DbSet<Role> Roles { get; set; }
}

Then based on what Scott suggested I created a Initializer class inheriting from RecreateDatabaseIfModelChanges.

Then in that class I add some dummy items like this:

    protected override void Seed(BackboneDbContext context)
    {
        var roles = new List<Role>
        {
            new Role
                {
                    RoleId = 0,
                    RoleName = "User",
                    RoleDescription = "This role belong to normal users.",
                }

        };

        roles.ForEach(r => context.Roles.Add(r));

        var users = new List<User>
        {
            new User  {UserId = 1, 
                       UserName = "Elham", 
                       Email = "[email protected]", 
                       Password = "xyz",
                       Roles = new List<Role>
                                   {
                                      roles[0]
                                   }

                       }

        };

        users.ForEach(u => context.Users.Add(u));
    }

I hope it make sense up to here. If not, basically the above code populate the tables with dummy data if database schema changes.

so far everything is absolutely great. I get the following tables:

Roles, Roles_Users and Users

they all have the info I need, but the problem is when I use the following LINQ query in my Repository class to get all the USers:

    public IQueryable<User> GetAllUsers()
    {
        IQueryable<User> allUsers = from u in _backboneDbContext.Users select u;

        return allUsers;
    }

now if I check allUsers before passing it to View, I get my users but the Role is set to 'Null'

I don't know why... Any Ideas ? Thank you.

Answer 1

You have to add a [System.ComponentModel.DataAnnotations.Association] attribute. For example:

public class User
{
    // [...]

    [System.ComponentModel.DataAnnotations.Association("User_Roles", "UserId", "RoleId")]
    public ICollection<Role> Roles { get; set; }
}

public class Role
{
    // [...]

    [System.ComponentModel.DataAnnotations.Association("Role_Users", "RoleId", "UserId")]
    public ICollection<User> Users { get; set; }
}

If the association is intended to be bi-directional, you must add this attribute on both the User.Roles and the Role.Users properties.

Answer 2

Try making your ICollection properties virtual. This allows EF to do lazy loading of the relationship. Alteratively, look into using the Include method on the query to eagerly load related entities.