Manipulating of Message Header in Silverlight

     Service proxy = new Service();

     proxy.OnOperationCompleted +=
          new EventHandler<DoWorkCompletedEventArgs>(onCompleted);

     using (OperationContextScope ctx=
     new OperationContextScope(proxy.InnerChannel))
     {

        OperationContext.Current.OutgoingMessageHeaders.Add
        (MessageHeader.CreateHeader("SomeHeader",
         "http://daenet.eu", "..."));

         proxy.OperationkAsync("foo");
     }

void onCompleted(IAsyncResult result)
{
     Service proxy = (Service1)result.AsyncState;

     using (OperationContextScope ocs =
     new OperationContextScope(((Service1Client)proxy).InnerChannel))
     {

          string res = proxy.EndDoWork(result);

          string header=
          OperationContext.Current.IncomingMessageHeaders.GetHeader<string>
          ("SomeHeader", "http://daenet.eu");
     }
}