private void btnOK_Click(object sender, EventArgs e)
        {
            if (!SpecialSetting.IsValidText(textEditor.RichTextBox.Text))
            {
                Messages.ShowWarningOk(this, SpecialSetting.WarningText);
                textEditor.Focus();
                return;
            }

            TargetRule   = SpecialSetting.ParseFrom(textEditor.RichTextBox.Text);
            DialogResult = DialogResult.OK;
        }