private void EditButton_Click(object sender, RoutedEventArgs e)
        {
            Invoice selectedItem = (Invoice)invoiceDataGrid.SelectedItem;

            if (selectedItem != null)
            {
                var newProduct = new InvoiceDetailWindow(selectedItem);

                if (newProduct.ShowDialog() == true)
                {
                }
            }
        }
        private void invoiceDataGrid_MouseDoubleClick(object sender, MouseButtonEventArgs e)
        {
            DataGridRow row = ItemsControl.ContainerFromElement((DataGrid)sender, e.OriginalSource as DependencyObject) as DataGridRow;

            if (row != null)
            {
                Invoice selectedItem = (Invoice)row.Item;

                var newProduct = new InvoiceDetailWindow(selectedItem);

                if (newProduct.ShowDialog() == true)
                {
                }
            }
        }