public static CurrentMessageContext Open(EndpointAddress returnAddress, string correlationId)
 {
   return _current = new CurrentMessageContext(returnAddress, correlationId, _current);
 }
 public void Dispose()
 {
   _current = _parentContext;
 }
 public CurrentMessageContext(EndpointAddress returnAddress, string correlationId, CurrentMessageContext parentContext)
 {
   _returnAddress = returnAddress;
   _correlationId = correlationId;
   _parentContext = parentContext;
 }