title: How do I return a string from WCF Workflow (WF4) when invoked by a Interface with ChannelFactory?
body: <p>If I have a workflow hosted (WF4 + WCF) and running in IIS implementing the following interface:</p>
  
  <pre><code>[ServiceContract]
  public interface IMessageService
  {   
       [OperationContract]
       string SendMessage(string message);
  }
  </code></pre>
  
  <p>(Using <code>RecieveActivity</code> and <code>SendReply</code> from <code>System.ServiceModel.Activities</code>)</p>
  
  <p>And invoke it like this:</p>
  
  <pre><code>    var channel = new ChannelFactory&lt;IMessageService&gt;().CreateChannel(&lt;init params&gt;);
      string answer = channel.SendMessage("Testmessage");
  </code></pre>
  
  <p>Then <code>answer</code> is always null. If I consume the workflow through the WcfTestClient I can see there is an returned xml object.</p>
  
  <blockquote>
    <p>How can I make the workflow return a string to populate <code>answer</code>?</p>
  </blockquote>
  
  <p>(I'd like to avoid the "Add a ServiceReference and return a lot of xml-approach")</p>