title: Linq - check condition in where clause if field can be null
body: <p>I have question - how to check condition in where clause even when item has no reference?</p>
  
  <p>Most basic way - I am checking field from my Class, which can be null. When I just check it in that way it will return Null Reference Exception</p>
  
  <pre><code> var soldOutProducts = from p in list 
              where p.destinataire.StartsWith("D") 
              select p; 
  </code></pre>