title: namespaces: using System & using System.IO
body: <p>so my program has these 2 lines at the beginning</p>
  
  <pre><code>using System;
  using System.IO;
  </code></pre>
  
  <p>Question: Is the second statement actually necessary  to include Sytem.IO methods and properties in my code?
   It seems that 'System.IO'  is  a 'child' of the namespace 'System'. Shouldn't the first line grab all the child namespaces too? Or Do I not understand namespaces correctly? </p>