Use String.Equals instead of String.Compare for equality checks

Per the [Best Practices for Using Strings in the .NET Framework](http://msdn.microsoft.com/en-us/library/dd465121(v=vs.110).aspx):

* Use an overload of the `String.Equals` method to test whether two strings are equal.
* Use the `String.Compare` and `String.CompareTo` methods to sort strings, **not to check for equality**.