title: Linq .FirstOrDefault not working
body: <p>I have a database where if the selected dvd's is not taken back (so the date of the arrival is empty) it should write to the linklabel that that the dvd is still rented:</p>
  
  <pre><code>var j = (from s in db.Rentals where s.MovieTitle == tb_movietitle.Text 
           select s.takenbackdate).FirstOrDefault();
  
  if (j == null)
  {
      linkLabel1.Text = "The dvd is still rented";
  }
  else
  {
      linkLabel1.Text = "Rentable";
  }
  </code></pre>
  
  <p>If I use <code>First()</code> it says that it is empty, but if I use <code>FirstOrDefault()</code> it shows <code>null</code> to all movies even if they have taken back date in the database.</p>