How can i assign multiple classes to xmldocument object?

I am creating a one service for Inserting(POST) data,

using this service client enter the data after that call service method to store that data in file (XML or JSON) in system

public void Add(Employee newEmployee)
        {
            XDocument doc = XDocument.Load(HttpContext.Current.Server.MapPath("StudentDB.xml"));
doc.Element("Employees").Add(
Department de=new Department();
            doc.Element("Employees").Add(
                new XElement("Employee",
                    new XElement("EmpId",newEmployee.EmpNo),
                    new XElement("EmpName",newEmployee.EmpName),
                    new XElement("DeptName",newEmployee.DeptName),
                new XElement("Department",
                    new XElement("DeptNo", de.DeptNo),
                    new XElement("Dname", de.Dname),
                    new XElement("Location", de.Location)
                )));

 doc.Save(HttpContext.Current.Server.MapPath("StudentDB.xml"));
        }

anilbabu