title: DataContractJsonSerializer not serializing properly
body: <p>I am trying to serialize some data which contains an observable collection of objects and write it into a text tile. My output is [] and I do now know where I have made a mistake.</p>
  
  <p>my object code</p>
  
  <pre><code>public class ObjectList : ObservableCollection&lt;string&gt;, INotify...
  {
      public ObservableCollection&lt;string&gt; ObjectListInstance = new ObservableCollection&lt;string&gt;();
      public string Name;
  
      ... get set methods &amp; property changed method
  }
  </code></pre>
  
  <p>my IO code</p>
  
  <pre><code>using (Stream newStream = await Windows.Storage.ApplicationData.Current.LocalFolder.OpenStreamForWriteAsync("file.txt", Windows.Storage.CreationCollisionOption.ReplaceExisting))
  {
        DataContractJsonSerializer newDataContractJsonSerializer = new DataContractJsonSerializer(typeof(ObservableCollection&lt;ObjectList&gt;));
        newDataContractJsonSerializer.WriteObject(newStream, ObjectList);
  }
  </code></pre>
  
  <p>my code stub</p>
  
  <pre><code>    ObjectList newObjectList = new ObjectList();
          newObjectList.Name = "AAA NAME";
  
  
          newObjectList.ObjectListInstance.Add("ITEM 1");
          newObjectList.ObjectListInstance.Add("ITEM 2");
  
          bool status = await IOClass.IO.WriteCategory(newObjectList);
  </code></pre>