Extensions Methods are the base of LINQ implementation.
Mitsuru Furuta from Microsoft France show a neat way
to return default value from a dictionnary
http://blogs.msdn.com/mitsufu/archive/2008/05/07/astuce-faciliter-la-lecture-des-donn-es-d-un-dictionnaire-gr-ce-une-m-thode-d-extension.aspx
Thanks Mitsuru for this nice tip
