How can I compare 2 XML Documents

<ids>
        <id>1</id>
        <id>2</id>
        <id>5</id>
        <id>6</id>
        <id>7</id>
        <id>8</id>
        <id>9</id>
       </ids>
    </ids>

<ids>
    <id>1</id>
    <id>2</id>
    <id>7</id>
    <id>8</id>
    <id>9</id>
  </ids>

XDocument file1Doc = XDocument.Load("File1.xml");
XDocument file2Doc = XDocument.Load("File2.xml");

IEnumerable<string> file1Elements = from d in file1Doc.Descendants("Id")
                                    select d.Value;

IEnumerable<string> file2Elements = from d in file2Doc.Descendants("Id")
                                    select d.Value;

var difference = file1Elements.Except(file2Elements);

XDocument file1Doc = XDocument.Load("File1.xml");
XDocument file2Doc = XDocument.Load("File2.xml");

IEnumerable<string> file2Elements = from d in file2Doc.Descendants("Id")
                                    select d.Value;

var x = from include in file1Doc.Descendants("Id")
        where file2Elements.Contains(include.Value) != true
        select include;