title: C#: Detecting which application has focus
body: <p>I'm looking to create a C# application that changes content according to which application currently has focus. So if the user is using Firefox, my app would know that. Same for Chrome, Visual Studio, TweetDeck etc.</p>
  
  <p>Is this possible, and if so - how would I go about achieving it?</p>
  
  <p>I have a feeling I'm asking for to much - but it's worth a try.</p>
  
  <p>Many thanks in advance.</p>