public partial class Form1 : Form
    {
        skladEntities se = new skladEntities();
……
 public Form1()
        {
            InitializeComponent();
            firm_localBindingSource.DataSource = 
                                from ff in se.firm
                                           where ff is firm_local
                                                 select ff;
…...
 private void bindingNavigatorAddNewItem_Click(object sender, EventArgs e)
        {
            firm_local fl = firm_local.Createfirm_local(0, "1111", "2222");
            firm_localBindingSource.Add(fl);
……
 private void bindingNavigatorDeleteItem_Click(object sender, EventArgs e)
        {            
            firm_localBindingSource.RemoveCurrent();
….
 private void button1_Click(object sender, EventArgs e)
        {
            se.SaveChanges();
 

            firm_localBindingSource.DataSource = 
                                from ff in se.firm
                                                 select ff;

public partial class Form1 : Form
    {
        skladEntities se = new skladEntities();
        IBindingList bl;
…
...
bl= 
((from ff in se.firm
                   where ff is firm_local
                   select ff) as IListSource).GetList() as IBindingList;
firm_localBindingSource.DataSource =  bl;
…..
bl.Remove(firm_localBindingSource.Current as firm_local);

 public class Firm_LocalObservableCollection : BindingList<firm_local>
    {
        skladEntities se = new skladEntities();
        public Firm_LocalObservableCollection()
        {
            foreach (firm em in (from e1 in se.firm
                                 where e1 is firm_local                                             
                                               select e1))
                base.Add(em as firm_local);            
        }
         public virtual void Add(firm_local item)
        {
            base.Add(item);
            se.AddTofirm(item);
        }
 
        public virtual void Remove(firm_local item)
        {
            base.Remove(item);
            se.DeleteObject(item);
        }
.....