title: WCF RIA Services for POCO as a query parameter
body: <p>I define a method below in a DomainService class but get a compiler error:
  <strong>Parameter 'objectType' of domain operation entry 'GetPropertiesByGuiObject' must be one of the predefined serializable types</strong>.   </p>
  
  <pre><code>public IQueryable&lt;PropertyType&gt; GetPropertiesByGuiObject(ObjectType objectType)
  {
    return properTypeDA0.GetPropertiesByGuiObject(objectType).AsQueryable();
  }
  </code></pre>
  
  <p>ObjectType is a POCO class I defined .
  I have added the [Serializable] or  [DataContract] attribute to the ObjectType class definition but the error still exist.
  Can the parameter of a domain operation entry be a POCO object?</p>