title: ReadAsAsync - throws Exception Type is an interface or abstract class and cannot be instantated
body: <p>I have the below code that tries to get the Appication object from the web api service. I get the follwoing exception :</p>
  
  <blockquote>
    <p>InnerException = {"Could not create an instance of type BusinessEntities.WEB.IApplicationField. Type is an interface or abstract class and cannot be instantated. Path '_applicationFormsList[0]._listApplicationPage[0]._listField[0]._applicationFieldID', line 1, position 194."}. </p>
  </blockquote>
  
  <p>I do not understand why changing the FieldList to an Interface is causing problems in deserializing the object. Any pointers are much appreciated.</p>
  
  <pre><code>Task&lt;HttpResponseMessage&gt; task = HttpClientDI.GetAsync(someUri);
  HttpResponseMessage response = task.Result;
  
  HttpClientHelper.CheckResponseStatusCode(response);
  
  try
  {
      Application application = response.Content.ReadAsAsync&lt;ApplicationPage&gt;().Result;
      return application;
  }
  catch (Exception ex)
  {
      throw new ServiceMustReturnApplicationException(response);
  }
  
  
  
  [Serializable]
  public class ApplicationPage
  {
      #region Properties
      public int PageOrder { get; set; }
      public string Title { get; set; }
      public string HtmlPage { get; set; }
      public int FormTypeLookupID { get; set; }
  
      List&lt;IApplicationField&gt; _listField = new List&lt;IApplicationField&gt;(); 
      public List&lt;IApplicationField&gt; FieldList
      {
          get { return _listField; }
          set { _listField = value; }
      }
  }
  </code></pre>