title: Correct SerializeObject method run?
body: <p>I added json dll in my project and try serialize object:</p>
  
  <pre><code> ProductType itemToEdit = new ProductType("Name");
   string jsonString = JsonConvert.SerializeObject(itemToEdit);
  </code></pre>
  
  <p>Error appears:</p>
  
  <blockquote>
    <p>An exception of type
    'System.MissingMethodException'
    occurred in Newtonsoft.Json.DLL but
    was not handled in user code</p>
    
    <p>Additional information: Method not
    found: 'Boolean
    System.Runtime.Serialization.DataContractAttribute.get_IsReference()'.</p>
  </blockquote>
  
  <p>But project builds correctly.</p>