public class CallToAction
{
    abstract class CSharpDeveloper { }
    class You : CSharpDeveloper { }
    string ReadTheContentOf(System.Uri url) { return string.Empty; }
    System.Uri URL = new System.Uri("http://stackoverflow.com/questions/9033/hidden-features-of-c");

    public CallToAction()
    {
        var you = new You();

        if (you is CSharpDeveloper)
            ReadTheContentOf(this.URL).AndLearnTonsOfStuffs();
    }
}

public static class MyExtensions
{
    public static void AndLearnTonsOfStuffs(this string input) { }
}

”This compiles by the way.  It won’t do squat, but it compiles!!“

Go spend half a day or a day and read that post, all the answers, the comments and the links within it.  I promised you won’t regret it and you might actually learn a thing or two about C# that you don’t know about.  I know I did.

Hint: the URL in the code above is actually clickable if you didn’t notice.  Or if you are hyperlink-challenged, you can cut and paste the following URL to your browser:
http://stackoverflow.com/questions/9033/hidden-features-of-c

Enjoy…