For the people who know me a little it's no surprise, but in case you didn't know: I love algorithms. I think they're the cornerstone of good software and they should be your first source of wisdom for every piece of software you're creating. This post will show an example of what I mean by that and how easy it is if you have a set of algorithms at your disposal which are solid, proven and correct.
In .NET there's a class called StringComparer. It has some handy helpers, like the InvariantCultureIgnoreCase StringComparer. These classes also implement a method called GetHashCode(string), which produces the hashcode in the scope of the comparer, so if you're calling that method on the InvariantCultureIgnoreCase variant, you get the hashcode for that scope.