private void chkHistory_Checked(object sender, RoutedEventArgs e) { try { if (CDeclaration.IsBusy || CPerformDrop.IsBusy) { MessageBox.ShowBox("MessageID368", BMC_Icon.Information); e.Handled = false; return; } chkHistory.IsEnabled = false; pnlDropContent.Children.Clear(); CDropHistory history = new CDropHistory(); pnlDropContent.Children.Add(history); history.Margin = new Thickness(0); } finally { chkHistory.IsEnabled = true; } }