Entity Framework, updating entity exception

Question

I am having following classes:

public class LbsNetwork : BaseEntity
{
    public virtual Guid Uuid { get; set; }

    public virtual string Name { get; set; }

    public virtual  string Description { get; set; }

    [InverseProperty("Network")]
    public virtual ICollection<LbsSubNetwork> SubNetworks { get; set; } 
}

 public class LbsSubNetwork:BaseEntity
{
    public virtual int ForeignId { get; set; }

    public virtual string Name { get; set; }

    public virtual string Description { get; set; }

    public virtual int Major { get; set; }

    [InverseProperty("SubNetworks")]
    [Required]
    public virtual LbsNetwork  Network { get; set; }

    [InverseProperty("SubNetwork")]
    public virtual ICollection<LbsDevice> Devices { get; set; } 
}

public class LbsDevice:BaseEntity
{
    public virtual string Name { get; set; }

    public virtual string Description { get; set; }

    public virtual int Minor { get; set; }

    public virtual int ForeignId { get; set; }

    [InverseProperty("Devices")]
    [Required]
    public virtual LbsSubNetwork SubNetwork { get; set; }

    public virtual BeaconProximity Proximity { get; set; }
}

And following code in DbContext:

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        modelBuilder.Entity<LbsNetwork>().ToTable("LbsNetworks");
        modelBuilder.Entity<LbsNetwork>().HasMany<LbsSubNetwork>(x=>x.SubNetworks)
            .WithRequired(x=>x.Network).HasForeignKey(x=>x.ForeignId).WillCascadeOnDelete();
        modelBuilder.Entity<LbsSubNetwork>().HasMany<LbsDevice>(x=>x.Devices)
            .WithRequired(x=>x.SubNetwork).HasForeignKey(x=>x.ForeignId).WillCascadeOnDelete();
    }

When i am trying to update existing entity of LbsNetwork in storage, then i am recieving next exception in Context.Save() method: "System.Data.Entity.Validation.DbEntityValidationException : Propetry: Network, Message: Network is required."

I think that there is a problem with one-to-many relations in entities. I am using next code to update entity:

    public void Update(LbsNetwork network)
    {
        Context.LbsNetworks.Attach(network);
        ((DbContext)Context.GetRealization()).Entry(network).State = EntityState.Modified;
        Context.Save();
    }

I'll be very grateful if you give me my mistakes. Thank you.

Answer 1

[InverseProperty("SubNetworks")]
[Required]
public virtual LbsNetwork  Network { get; set; }

This cause the problem on your query. I don't think it's a good idea to put a Required validation attribute in a navigation property. You should put it in a foreign key instead.

[InverseProperty("SubNetworks")]
public virtual LbsNetwork  Network { get; set; }