if exists XML Element

from the below code

How do i find, if there EXISTS an xmlElemenent MiddleName(i am not asking for value) before i evaluate it

something like if exists(MiddleName) then.....

Sometimes in my xml the attribute(not the value) might not exists

public static string ProcessXMLdata(XElement xml)

{

try

{

string processResult;

XNamespace ns = "http://schemas.datacontract.org/2004/07/BondData.Shared.DataModels.Peoplehouse";

if (xml.Element(ns + "FirstName").Value == null ||

xml.Element(ns + "LastName").Value == null ||

xml.Element(ns + "MiddleName").Value == null ||

xml.Element(ns + "ApplicantAddress").Value == null ||