private void button_Click(object sender, RoutedEventArgs e) { try { if (textBox.Text == "" || textBox_Copy.Text == "" || textBox_Copy1.Text == "" || textBox_Copy2.Text == "" || textBox_Copy3.Text == "" || textBox_Copy4.Text == "") { throw new ArgumentNullException("You need to fill all fields"); } bl.AddRequest(req); MessageBox.Show("Added"); req = new GuestRequest(); this.DataContext = req; } catch (Exception ex) { MessageBox.Show(ex.Message); } }