Entity Framework Code First Mapping

Question

I have two classes, the Group class has a many to many relationship with the User class (representing the groups a user belongs to) and then the group also has a relationship of one to many with the user class (representing the owner of a group).

How can I map this?

public class User
{
    public int Id { get; set; }
    public string Avatar { get; set; }
    public string Name { get; set; }
    public string Message { get; set; }

    public virtual ICollection<Group> OwnedGroups { get; set; }
    public virtual ICollection<Group> Groups { get; set; }
}

public class Group
{
    public int Id { get; set; }
    public DateTime CreateDate { get; set; }
    public DateTime ModifyDate { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public bool System { get; set; }
    public int ViewPolicy { get; set; }
    public int JoinPolicy { get; set; }
    public string Avatar { get; set; }
    public int Order { get; set; }
    public int GroupType { get; set; }

    public virtual User Owner { get; set; }
    public virtual ICollection<User> Members { get; set; }
}

tks in advance!

Ladislav Mrnka · Accepted Answer · 2011-04-19 18:51:56Z

5

I would use fluent API:

public class Context : DbContext
{
    public DbSet<User> Users { get; set; }
    public DbSet<Group> Groups { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<User>()
                    .HasMany(u => u.Groups)
                    .WithMany(g => g.Members);

        modelBuilder.Entity<User>()
                    .HasMany(u => u.OwnedGroups)
                    .WithRequired(g => g.Owner)
                    .WillCascadeOnDelete(false);
    }
}

It should also be possible with Data annotations:

public class User
{
    ...

    [InverseProperty("Owner")]
    public virtual ICollection<Group> OwnedGroups { get; set; }
    [InverseProperty("Members")]
    public virtual ICollection<Group> Groups { get; set; }
}

public class Group
{
    ...

    [InverseProperty("OwnedGroups")]
    public virtual User Owner { get; set; }
    [InverseProperty("Groups")]
    public virtual ICollection<User> Members { get; set; }
}

InverseProperty is not needed on both sides of relation but it does definition clearer.

edited Apr 19, 2011 at 18:51

answered Apr 19, 2011 at 18:43

Ladislav Mrnka

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1 Comment

Rusi Nova Over a year ago

@Ladislav Mrnka can u explain WillCascadeOnDelete and WithRequired. Plz. thanx!!

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