title: Removing duplicates from a list of tuples
body: <p>I have a list of <code>Tuple&lt;string,string&gt;</code> objects and I want to remove duplicates where, for example, the tuples <code>(a,b)</code> and <code>(b,a)</code> are considered the same (these are the edges of a graph). What is a <em>nice</em> way to do this ?</p>