private async void FilterList()
        {
            string item = PkrRefVal.Items[PkrRefVal.SelectedIndex];

            if (item != "All")
            {
                foreach (var record in AppData.PropertyModel.SelectedProperty.RequestGroups)
                {
                    foreach (var res in record.Records)
                    {
                        if (res.Record.RefVal == item)
                        {
                            DocumentViewModel.RefVal = res.Record.KeyVal;
                        }
                        break;
                    }
                }

                _lstDocuments = new ObservableCollection <DocumentViewModel>(await _documentListModel.GetFilteredDocumentList());
                Lstvw_Documents.ItemsSource = _lstDocuments;
            }
            else
            {
                _lstDocuments = new ObservableCollection <DocumentViewModel>(await _documentListModel.GetDocumentList());
                Lstvw_Documents.ItemsSource = _lstDocuments;
            }
        }