What is the best way to compare XML files for equality?

I ended up getting the result I wanted with the following code:

private static void ValidateResult(string validationXml, XPathNodeIterator iterator, params string[] excludedElements)
    {
        while (iterator.MoveNext())
        {
            if (!((IList<string>)excludedElements).Contains(iterator.Current.Name))
            {
                Assert.IsTrue(validationXml.Contains(iterator.Current.Value), "{0} is not the right value for {1}.", iterator.Current.Value, iterator.Current.Name);
            }
        }
    }

Before calling the method, I create a navigator on the instance of XmlDocument this way:

XPathNavigator nav = xdoc.CreateNavigator();

Next, I create an instance of XPathExpression, like so:

XPathExpression expression = XPathExpression.Compile("/blah/*");

I call the method after creating an iterator with the expression:

XPathNodeIterator iterator = nav.Select(expression);

I'm still figuring out how to optimize it further, but it does the trick for now.