private void updateClient_Click(object sender, RoutedEventArgs e) { if (this.mangaclientgrid.SelectedItems.Count != 1) { MessageBox.Show("Select 1 client to update"); return; } client = (Client)this.mangaclientgrid.SelectedItem; if (client == null) { MessageBox.Show("Please select a client to update"); } AddClient add = new AddClient(client); add.Closed += AddClient_close; add.ShowDialog(); }