title: WCF custom object returns correctly apart from returning empty Lists
body: <p>I send XML to my webservice and the receiving method is:</p>
  
  <pre><code>public XElement SubmitRecipe(Recipe recipe)
  </code></pre>
  
  <p>The recipe parameter is correctly receiving all properties but recipe.Allergies has a count of 0, does anyone know why?</p>
  
  <p>Sample XML file:</p>
  
  <pre><code>&lt;Recipe&gt;
  &lt;Allergies&gt;
      &lt;Allergy&gt;nuts&lt;/Allergy&gt;
      &lt;Allergy&gt;wheat&lt;/Allergy&gt;
  &lt;/Allergies&gt;
  &lt;Title&gt;recipe title&lt;/Title&gt;
  &lt;Id&gt;107&lt;/Id&gt;
  &lt;/Recipe
  </code></pre>
  
  <p>The Recipe object:</p>
  
  <pre><code>[CollectionDataContract(Name = "Allergies", ItemName = "Allergy")]
  public class AllergyList : List&lt;string&gt; { }
  
  [DataContract]
  public class Recipe
  {        
      [DataMember(Name = "Allergies")]
      public AllergyList Allergies { get; set; }
  
      [DataMember]
      public int Id { get; set; }
  
      [DataMember]
      public string Title { get; set; }
  }
  </code></pre>
  
  <p>In my create method test I get what I expect:</p>
  
  <pre><code>public Recipe GetRecipe()
  {
      Recipe recipe = new Recipe();
  
      recipe.Id = 1;
      recipe.Allergies = new AllergyList();
      recipe.Allergies.Add("nuts");
      recipe.Allergies.Add("wheat");
  }
  
  &lt;Recipe&gt;
      &lt;Allergies&gt;
          &lt;a:Allergy&gt;nuts&lt;/a:Allergy&gt;
          &lt;a:Allergy&gt;wheat&lt;/a:Allergy&gt;
      &lt;/Allergies&gt;
      &lt;Id&gt;1&lt;/Id&gt;
  &lt;/Recipe&gt;
  </code></pre>