NaklDataContext db;
        private void Form2_Load(object sender, EventArgs e)
        {
            db = new NaklDataContext();
            nakldoc = db.Nakls.First<Nakl>(n => n.id == id);
            naklBindingSource.DataSource = nakldoc;    
            naklDtlsBindingSource.DataSource = nakldoc.NaklDtls;
            
        }

 partial class NaklDtl
    {
        public bool HasErrod = false;

        partial void OnamountChanging(decimal? value)
        {
            Checked_amount(value);
        }

        private void Checked_amount(decimal? value)
        {
            if (!value.HasValue) HasErrod = true;
            else if (value.Value ==  0 ) HasErrod = true;
            else HasErrod = false;
        
        }
        partial void OnValidate(ChangeAction action)
        {             
            Checked_amount(this.amount);
            if (HasErrod) throw new Exception("Нет количества!");
        }

    }

  db.SubmitChanges();

          string s;
            foreach (NaklModel.NaklDtl o in CurrentHdr.NaklDtl) 
            {

                var state = context.ObjectStateManager.GetObjectStateEntry(o.EntityKey);
                if (state.EntityKey.EntityKeyValues == null)
                    s = "null";
                else if (state.EntityKey.EntityKeyValues[ 0 ] == null)
                    s = "null";
                else
                    s = state.EntityKey.EntityKeyValues[ 0 ].ToString();
                MessageBox.Show(String.Format("{0}={1}",s, state.State));
            }