private void Compare_Click(object sender, RoutedEventArgs e) { if (_firstPath == null || _secondPath == null) { WarningWindow worningWindow = new WarningWindow("Choose two files !!!", this); worningWindow.Show(); } else { try { var result = _fileComparer.Compare(ComparerType.Custom, _firstPath, _secondPath); TextBlock.Text = result; } catch (Exception ex) { TextBlock.Text = ex.Message; } } }