title: LINQ to SQL - nullable types in where clause
body: <p>I have a table with a column that has null values... when I try to query for records where that column IS NULL:</p>
  
  <p>THIS WORKS:</p>
  
  <pre><code>
  
          var list = from mt in db.MY_TABLE
                     where mt.PARENT_KEY == null
                     select new { mt.NAME };
  
  </code></pre>
  
  <p>THIS DOES NOT:</p>
  
  <pre><code>
  
          int? id = null;
          var list = from mt in db.MY_TABLE
                     where mt.PARENT_KEY == id
                     select new { mt.NAME };
  
  </code></pre>
  
  <p>Why?</p>