title: Automapper child entities not mapping
body: <p>Im trying to map a parent entity that includes a default child entity.</p>
  
  <p>So, I have a <code>promotion</code> object, that has a collection of <code>localisedPromotion</code> objects</p>
  
  <p>I want to set a specific <code>localisedPromotion</code> and set it as my <code>defaultLocalisedPromotion</code></p>
  
  <p>In my config I have:</p>
  
  <pre><code>config.CreateMap&lt;LocalisedPromotion, LocalisedPromotionViewModel&gt;()
      .ForMember(dest =&gt; dest.LocalisedPromotionId, o =&gt; o.MapFrom(src =&gt; src.Id));
  
  config.CreateMap&lt;Promotion, PromotionViewModel&gt;()
      .ForMember(dest =&gt; dest.DefaultLocalisedPromotion,
                 o =&gt; o.MapFrom(src =&gt; src.LocalisedPromotions
                                          .FirstOrDefault(x =&gt; x.CultureId == src.DefaultCultureId)));
  </code></pre>
  
  <p>So in my mind this should set the field <code>DefaultLocalisedPromotion</code> of type <code>LocalisedPromotionViewModel</code> </p>
  
  <p>However the field is always null</p>
  
  <p>Is there an obvious way of doing what I am trying to achieve</p>