WPF datagrid new row event

Hi everyone I use Visual Studio 2012 with c# and wpf.

I have a datagrid and in it I enabled editing and adding new rows. Now I have to distinguish between the two so I can direct them to the separate methods for updating or inserting into the database. I tried using the observable collection's collection changed method:

 void Opcine_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
            {
                if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
                {
                    Opcina opc = new Opcina();
                        opc.IsNew = true; 
                }
            }

And it hits. The problem is that I set the IsNew to true but when it comes time to save stuff by clicking on a button the IsNew is set to false for all the rows including the new one. What am I doing wrong?

My save method:

 public void SpasiOpcinu()
               {
                foreach (Opcina opc in _opcine)
                {
                    _opcina = opc;

                    if (opc.IsNew==true)

                    {
                    _glavniRepository.SpasiOpcinu(_opcina);
                    opc.IsNew = false;
                    }

                    else 

                   {
                   _glavniRepository.IzmijeniOpcinu(_opcina);
                   }
               }
               }