private void btnEditEvent_Click(object sender, EventArgs e) { //Close Attendee Panels If Open subEventViewer.hidePanelViewEditAttendeesPersonal(); subEventViewer.hidePanelViewEditAttendeesManager(); subEventViewer.hidePanelCheckAvailabilityAttendees(); //USAGE ERROR CHECKING int selectedIndex = subEventViewer.checkedListBox1.SelectedIndex; if (selectedIndex == -1) { DialogResult Error = MessageBox.Show("No events are selected.", "Error", MessageBoxButtons.OK); return; } subEventViewer.showSubEventControlsEdit(); }