title: Linq select one occurrence
body: <p>how can I use link to fetch one-to-one relation that does not contain duplicates? Example:</p>
  
  <p><strong>ID</strong> |  <strong>STATUS</strong></p>
  
  <p>1 |   CHECKIN</p>
  
  <p>2 |   CHECKOUT</p>
  
  <p>2 |   CHECKOUT</p>
  
  <p>1    |   CHECKIN</p>
  
  <p><strong>3   |    CHECKOUT</strong> &lt;--</p>
  
  <p>I should only retrieve the <strong>ID 3 CHECKOUT</strong>  because he is not duplicated.</p>
  
  <p>Can you help me using linq?</p>