XML : Creating Xml Dynamically From Object

Here I have a scenario that Create xml file dynamically and it should be serialisable. xml is like:

  <person>      <personaldata>          <name>gopi</name>          <lastname>ch</lastname>      </personaladata>      <Educationaladata>          <Graduation>b.tech</graduation>          <designation>Engineer</designation>      </educationaldata>  </person>    

person class has name, lastname, designation, graduation and properties

I tried this

  public string CreateXmlObject(Person objPerson)      {      var objXmlDocument = new XmlDocument();      var objXpath = objXmlDocument.CreateNavigator();      var objXmlSeialiser = new XmlSerializer(objPerson.GetType());      using (var xs = objXpath.AppendChild())      {          objXmlSeialiser.Serialize(xs, objPerson);      }      return objXmlDocument.OuterXml;  }    

My Problem is I have to read Specific data from Xml And Update Specific data to Xml . I want to read only Personaldata when i update, update should only apply to Personaldata Not Otherdata