private void ButtonFile_Click(object sender, RoutedEventArgs e) { string source, destination; source = TextBoxFileSource.Text; destination = TextBoxFileDestination.Text; if (string.IsNullOrEmpty(source)) { throw new Exception("Source cannot be empty."); } if (string.IsNullOrEmpty(destination)) { throw new Exception("Destination cannot be empty."); } try { Task.Run(() => _listener.SendFileAsync(_client.Id, source, destination, false)); } catch (Exception ex) { MessageBox.Show(ex.Message, "Error", MessageBoxButton.OK, MessageBoxImage.Error); } }