private void DialogOkClicked(object sender, RoutedEventArgs e)
        {
            string opStr = TypeValueOperator.SelectedItem as string;

            _operator = FilterValue.GetOpFromDescr(opStr);
            if (TypeExtractor.IsString(_kind))
            {
                _valStr = TbTypeValue.Text;
                _valObj = _valStr;
                if ((bool)TypeValueCase.IsChecked)
                {
                    _operator |= FilterValue.Op.IGNORECASE;
                }
                if ((bool)TypeValueRegex.IsChecked)
                {
                    _operator |= FilterValue.Op.REGEX;
                    try
                    {
                        Regex regex = new Regex(_valStr);
                    }
                    catch (ArgumentException ex)
                    {
                        GuiUtils.ShowError(ex, this);
                        return;
                    }
                }

                DialogResult = true;
                return;
            }
            _valStr = TbTypeValue.Text.Trim();
            if (TypeExtractor.GetTypeFromString(_valStr, _kind, out _valObj))
            {
                DialogResult = true;
                return;
            }
            MessageBox.Show("String format of the value is invalid.", "INVALID FORMAT", MessageBoxButton.OK, MessageBoxImage.Error);
        }