title: LINQ: check whether two list are the same
body: <p>This should be easy.</p>
  
  <p>I want to check whether two list are the same in that they contain all the same elements or not, orders not important. </p>
  
  <p>Duplicated elements are considered equal, i.e.e, <code>new[]{1,2,2}</code> is the same with <code>new[]{2,1}</code></p>