WCF service returns XML or JSON-formatted data

The first way
public string GetData (string format)
{
string res = null;
Student stu = new Student
{
Stuid = 3,
Stuname = "John Doe"
};
using (MemoryStream ms = new MemoryStream ())
{
Xmlobjectserializer sz = null;
if (format. ToLower () = = "xml")
{
SZ = new DataContractSerializer (stu. GetType ());
}
Else
{
SZ = new DataContractJsonSerializer (stu. GetType ());

}
Sz. WriteObject (MS, Stu);
res = Encoding.UTF8.GetString (Ms. ToArray ());
}
return res;
}
The second way
Public Message GetData (string format)
{
Weboperationcontext context = weboperationcontext.current;
Student stu = new Student
{
Stuid = 222,
Stuname = "Zhang San"
};
Message Msgreturn = null;
if (format. ToLower () = = "xml")
{
Msgreturn = context. Createxmlresponse<student> (Stu);
}
Else
{
Msgreturn = context. Createjsonresponse<student> (Stu);
}

return msgreturn;
}

[DataContract]
public class Student
{
[DataMember (name= "ID")]
public int Stuid {get; set;}

[DataMember (Name = "Stu_name")]
public string Stuname {get; set;}
}

WCF service returns XML or JSON-formatted data