如何从基于REST的WCF服务读取Authorization标头？

<bindings>
  <webHttpBinding>
   <binding name="RESTBinding">
     <security mode="TransportCredentialOnly">
       <transport clientCredentialType="Basic" />
      </security>
    </binding>
  </webHttpBinding>
</bindings>

OperationContext operationContext = OperationContext.Current;
MessageHeaders headers = operationContext.IncomingMessageHeaders;
string authorizationHeader = headers.GetHeader<string>("Authorization", "http://schemas.microsoft.com/ws/2005/05/identity/claims/Authorization");