在使用UserNamePasswordValidator时，如何在WCF服务中获取SOAP用户名？

<behaviors>
  <serviceBehaviors>
    <behavior name="CustomValidatorBehavior">
      <serviceCredentials>
        <userNameAuthentication userNamePasswordValidationMode="Custom"
                                customUserNamePasswordValidatorType="YourNamespace.YourValidatorClass, YourAssembly" />
      </serviceCredentials>
    </behavior>
  </serviceBehaviors>
</behaviors>

<services>
  <service name="YourNamespace.YourServiceClass">
    <endpoint address="" binding="basicHttpBinding" contract="YourNamespace.YourServiceInterface"
              behaviorConfiguration="CustomValidatorBehavior" />
  </service>
</services>

public class YourServiceClass : YourServiceInterface
{
    public void YourServiceMethod()
    {
        MessageHeaders headers = OperationContext.Current.IncomingMessageHeaders;
        string username = headers.GetHeader<string>("Username", "Namespace");
        // 使用获取到的用户名进行相应的处理
    }
}