private void cmbProduct_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            var cmb = sender as ComboBox;

            if (cmb.SelectedValue == null)
            {
                return;
            }

            var productId = int.Parse(cmb.SelectedValue.ToString());

            _returnPurchaseViewModel.SetProductPriceDetails(productId, ReturnPurchaseDataGrid.SelectedIndex);
        }