title: Portable Class Library does not support System.IO, Why?
body: <p>I created a <strong>portable class library</strong> to be used in my <strong>Monodroid project</strong>.
  But the problem is that I need <strong>System.IO</strong> library but unfortunately I couldn't add it.</p>
  
  <p>I even tried to add it by Add Reference option but it was in vain.</p>
  
  <p>Why this happened ?
  How shall I do this ?</p>