Microsoft.Practices.Prism question

Hello, I've had trouble obfuscating a few ViewModel classes. Ultimately, I discovered that since I serialize a few of said classes I had to exclude them from obfuscation because of the Obfuscation/Reflection issue.

This isn't a big deal. But I noticed I couldn't simply obfuscate Microsoft.Practices.Prism. I thought since my VM classes derive from NotificationObject, that it's probably that this class needed to be excluded. But turns out there are no public methods. So NotificationObject could be obfuscated.

Ok then, who's the culprit? I tracked it down to this class/method/code:

public class UriQuery : IEnumerable<KeyValuePair<string, string>>
    {
        private readonly List<KeyValuePair<string, string>> entries 
           = new List<KeyValuePair<string, string>>();

        public IEnumerator<KeyValuePair<string, string>> GetEnumerator()
        {
            return this.entries.GetEnumerator();
        }
    }

Can someone explain to me why the above code can't be obfuscated? Just curious...