title: IQueryable<T> vs IEnumerable<T> with Lambda, which to choose?
body: <p>I do more and more exercise with Lambda but I do not figure out why sometime example use <code>.AsQueryable();</code> that use the IQueryable and sometime it omit the <code>.AsQueryable();</code> and use the IEnumerable.</p>
  
  <p>I have read the <a href="http://msdn.microsoft.com/en-us/library/bb351562.aspx" rel="nofollow noreferrer">MSDN</a> but I do no see how "executing an expression tree" is an advantage over not.</p>
  
  <p>Anyone can explain it to me?</p>