private void button4_Click(object sender, EventArgs e) { if (lbSubjects.SelectedItem != null) { int id = ((Question)dgvQuestions.SelectedCells[0].OwningRow.DataBoundItem).ID; controller.DeleteQuestion(id); int selected = ((Subject)lbSubjects.SelectedItem).ID; dgvQuestions.DataSource = null; dgvQuestions.DataSource = controller.GetQuestions(selected); } }