How to Fill TreeView from DataBase

 class Hesabs:Hesab
    {
    public Hesabs()
    {
        AllHesab = new ObservableCollection<hesab>();
    }
    public ObservableCollection<hesab> AllHesab { get; set; }
           }

</hesab></hesab>

 public ObservableCollection<hesabs> AllHesab { get; set; }
    public ObservableCollection<hesabs> FirstHesab { get; set; }

    public ViewModelHesabs()
    { 
        CRMEntities crm=new CRMEntities();

        var ls = from h in crm.Hesab
                 where (h.FatherID == null)
                 select h;
        ObservableCollection<hesabs> hes = new ObservableCollection<hesabs>();
        foreach (Hesab hh in ls.ToList())
        {
            var ls2 = from h in crm.Hesab
                      where (h.FatherID == hh.ID)
                      select h;
            Hesabs hesab = new Hesabs();
            hesab.Name = hh.Name;
            hesab.ID = hh.ID;
            hesab.AllHesab = new ObservableCollection<hesab>(ls2.ToList());
            hes.Add(hesab);
        }
        FirstHesab = hes;
    }

</hesab></hesabs></hesabs></hesabs></hesabs>

<treeview itemssource="{Binding FirstHesab}">
     <treeview.itemtemplate>
     <hierarchicaldatatemplate itemssource="{Binding AllHesab}" datatype="         {x:Type local:Hesabs}">
             <stackpanel orientation="Horizontal">
                 <textblock text="{Binding Name}" tag="{Binding ID}" />
             </stackpanel>
         </hierarchicaldatatemplate>
     </treeview.itemtemplate>
 </treeview>