public NomenclatureViewModel() { this._Nomenclatures = new ObservableCollection <NomenclatureHedar>(FakeDataContext.GetAllNomenclatures()); this._NomenclatureFields = new ObservableCollection <NomeclatureMetaData>(FakeDataContext.GetNomenlatureFields(1)); this._Fields = new ObservableCollection <ObservableCollection <string> >(); var list = FakeDataContext.GetNomenclatureContent(1); foreach (var li in list) { var ader = new ObservableCollection <string>(li); _Fields.Add(ader); } }