title: Html.BeginCollectionItem only nested proeprties are null
body: <p>I use Html.BeginCollectionItem helper for getting an edited variable length list. It works for non-nested properties (string Member.Info, int Member.MotherID, etc.) but <strong>all nested ones are null</strong> (Mother Member.Mother, etc.)...</p>
  
  <p>Member class:</p>
  
  <pre><code> public class Member : Person
   {
      [Key] 
      public int MemberID { get; set; }
      ...
      public string Info { get; set; }
  
      public int MotherID { get; set; }
  
      public virtual Mother Mother { get; set; }
   }
  </code></pre>
  
  <p>Nested Mother class:</p>
  
  <pre><code> public class Mother : Person
   {
      [Key]
      public int MotherID { get; set; }
  
      public virtual ICollection&lt;Member&gt; Children { get; set; }
  
      public Mother()
      {
          Children = new List&lt;Member&gt;();
      }
  }
  </code></pre>
  
  <p>Controller snippet:</p>
  
  <pre><code> [HttpPost]
   public ActionResult GoSend(IEnumerable&lt;Member&gt; me) // Mother in 'me' is null
   {...}
  </code></pre>
  
  <p>Index.cshtml:</p>
  
  <pre><code> @model IEnumerable&lt;Directory_MVC.Models.Member&gt;
   ...
   @using (Html.BeginForm("GoSend", "Members", FormMethod.Post))
   {
      @foreach (var item in Model)
      {
          Html.RenderPartial("EditorRow", item);       
      }
   }
  </code></pre>
  
  <p>EditorRow.cshtml:</p>
  
  <pre><code> @model Directory_MVC.Models.Member
   ...
   @using (Html.BeginCollectionItem("me"))
   {
        @Html.HiddenFor(x =&gt; x.Info)
        @Html.HiddenFor(x =&gt; x.MotherID)
        @Html.HiddenFor(x =&gt; x.Mother)
        @Html.HiddenFor(x =&gt; x.Mother.Email)
   }
  </code></pre>
  
  <p>Generated HTML for that broken Mother input is:</p>
  
  <pre><code> &lt;input id="me_88c3c30f-3aa7-4729-9879-368f01073080__Mother" name="me[88c3c30f-3aa7-4729-9879-368f01073080].Mother" type="hidden" value="System.Data.Entity.DynamicProxies.Mother_5D771F511FE55BBA8F7C7D21A0054616D2EB9278EDCA1D59DFDCB1B68EA45920" /&gt;
  </code></pre>
  
  <p>Generated HTML for working MotherID input is:</p>
  
  <pre><code> &lt;input data-val="true" data-val-number="The field MotherID must be a number." data-val-required="The MotherID field is required." id="me_88c3c30f-3aa7-4729-9879-368f01073080__MotherID" name="me[88c3c30f-3aa7-4729-9879-368f01073080].MotherID" type="hidden" value="1" /&gt;
  </code></pre>
  
  <p>What am I doing wrong? <strong>Is it even possible to serialize that Mother object</strong> and retrieve it in that Controller via the Html.BeginCollectionItem?</p>