Although this is old post, I resolve like below:

/// <summary>
    /// Exports a module to xml
    /// </summary>
    /// <param name="ModuleID"></param>
    /// <returns></returns>
    public string ExportModule(int moduleID) {
     
      // constants
      const string StartTagformat = "<{0}>";
      const string EndTagformat = "</{0}>";
      const string Tagformat = "<{0}>{1}</{0}>";

      // init vars
      PortalSettings portalSettings = PortalController.GetCurrentPortalSettings();
      int tabID = portalSettings.ActiveTab.TabID;
      ModuleController objController = new ModuleController();
      ModuleInfo objModule = objController.GetModule(moduleID, tabID, false);

      Hashtable objSettings = objController.GetTabModuleSettings(objModule.TabModuleID);
      StringBuilder sbXml = new StringBuilder();
     
      // start xml
      sbXml.Appendformat(StartTagformat, RootElement);

      // save all keys     
      foreach (Object key in objSettings.Keys) {
        sbXml.Appendformat(Tagformat, Convert.ToString(key), XmlUtils.XMLEncode(Convert.ToString(objSettings[key])));
      }     

      // end xml
      sbXml.Appendformat(EndTagformat, RootElement);

      // return xml
      return sbXml.ToString();
    }

hope helps.