title: LINQ's WHERE clause where COLUMN may be null
body: <p>I have a problem with making WHERE clause with LINQ. I tried to google it but I've only got answers on what to do if the external variable is the type of nullable integer... well, I've tried these methods the other way around (I have 0...1 relations in my dataset):
  e.g.</p>
  
  <pre><code>int oldId = oldQuestion.id;
  IEnumerable&lt;possible_answer&gt; possibleAnswersQuery =
              from x in Mentor11Entities.possible_answers
              where object.Equals(x.question_id, oldId)
              select x;
  List&lt;possible_answer&gt; possibleAnswers = 
              possibleAnswersQuery.ToList&lt;possible_answer&gt;();
  </code></pre>
  
  <p>or</p>
  
  <pre><code>int oldId = oldQuestion.id;
  IEnumerable&lt;possible_answer&gt; possibleAnswersQuery =
              from x in Mentor11Entities.possible_answers
              where Convert.ToInt32(x.question_id ?? 0).Equals(oldId)
              select x;
  List&lt;possible_answer&gt; possibleAnswers = 
              possibleAnswersQuery.ToList&lt;possible_answer&gt;();
  </code></pre>
  
  <p>but I'm always getting the error that LINQ doesn't support certain functions... is there any way to get around the problem?</p>