error during serialization using json javascriprtserializer

Question

//controller
public JsonResult GetAllClient()
      {
          var product = GetClient().ToList();
          return Json(new { data = product }, JsonRequestBehavior.AllowGet);
      }

//WebConfig

<system.web.extensions>
    <scripting>
      <webServices>
        <jsonSerialization maxJsonLength="102400"/>
      </webServices>
    </scripting>
  </system.web.extensions>