如何修改WCF SOAP响应中Header的mustUnderstand值为0？

针对你的WCF服务返回的SOAP响应中，Action、Security等Header的mustUnderstand="1"导致Axis2客户端报错的问题，以下是具体解决方法：

1. 修改自定义MessageHeader的MustUnderstand值 #

如果是你自己定义的MessageHeader（比如示例中的ExtraValues），直接在[MessageHeader]属性中设置MustUnderstand=false即可：

[MessageHeader(
  Name = "OutOfBandData",
  Namespace = "http://www.examples.com",
  MustUnderstand=false // 改为false，对应SOAP中的0
)]
public string ExtraValues
{
  get { return extra; }
  set { this.extra = value; }
}

2. 修改WS-Addressing Action头的MustUnderstand值 #

WCF会自动添加WS-Addressing的Action头，要修改它的MustUnderstand属性，需要通过**自定义消息检查器（IDispatchMessageInspector）**拦截并修改响应：

步骤1：实现IDispatchMessageInspector #

public class MustUnderstandHeaderInspector : IDispatchMessageInspector
{
    public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
    {
        // 无需处理请求，返回null即可
        return null;
    }

    public void BeforeSendReply(ref Message reply, object correlationState)
    {
        // 查找Action头
        int actionIndex = reply.Headers.FindHeader("Action", "http://www.w3.org/2005/08/addressing");
        if (actionIndex != -1)
        {
            // 修改MustUnderstand为false，对应SOAP响应中的mustUnderstand="0"
            reply.Headers[actionIndex].MustUnderstand = false;
        }
    }
}

步骤2：实现IEndpointBehavior #

public class MustUnderstandBehavior : IEndpointBehavior
{
    public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters) { }

    public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime) { }

    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {
        // 将自定义检查器添加到服务端调度逻辑中
        endpointDispatcher.DispatchRuntime.MessageInspectors.Add(new MustUnderstandHeaderInspector());
    }

    public void Validate(ServiceEndpoint endpoint) { }
}

步骤3：配置服务端行为 #

可以通过代码或配置文件两种方式添加该行为：

代码配置方式

ServiceHost host = new ServiceHost(typeof(YourService));
foreach (ServiceEndpoint endpoint in host.Description.Endpoints)
{
    endpoint.Behaviors.Add(new MustUnderstandBehavior());
}
host.Open();

配置文件方式

先注册行为扩展：

<system.serviceModel>
  <extensions>
    <behaviorExtensions>
      <add name="mustUnderstandBehavior" type="YourNamespace.MustUnderstandBehaviorElement, YourAssembly" />
    </behaviorExtensions>
  </extensions>
  <!-- 端点行为配置 -->
  <behaviors>
    <endpointBehaviors>
      <behavior name="CustomEndpointBehavior">
        <mustUnderstandBehavior />
      </behavior>
    </endpointBehaviors>
  </behaviors>
  <!-- 服务配置 -->
  <services>
    <service name="YourNamespace.YourService">
      <endpoint address="" binding="wsHttpBinding" contract="YourNamespace.IYourService" behaviorConfiguration="CustomEndpointBehavior" />
    </service>
  </services>
</system.serviceModel>

对应的BehaviorElement实现：

public class MustUnderstandBehaviorElement : BehaviorExtensionElement
{
    public override Type BehaviorType => typeof(MustUnderstandBehavior);

    protected override object CreateBehavior()
    {
        return new MustUnderstandBehavior();
    }
}

3. 修改Security头的MustUnderstand值 #

如果Security头是WCF的WS-Security自动生成的，在上述BeforeSendReply方法中添加修改逻辑即可：

public void BeforeSendReply(ref Message reply, object correlationState)
{
    // 修改Action头
    int actionIndex = reply.Headers.FindHeader("Action", "http://www.w3.org/2005/08/addressing");
    if (actionIndex != -1)
    {
        reply.Headers[actionIndex].MustUnderstand = false;
    }

    // 修改Security头
    int securityIndex = reply.Headers.FindHeader("Security", "http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd");
    if (securityIndex != -1)
    {
        reply.Headers[securityIndex].MustUnderstand = false;
    }
}

原理说明 #

Axis2客户端报错的核心原因是：SOAP规范中mustUnderstand="1"要求客户端必须处理该Header，但你的Axis2客户端未实现Security头的处理逻辑。将mustUnderstand改为0（对应WCF中的false），即可告知客户端无需强制处理该Header，从而避免报错。

内容的提问来源于stack exchange，提问作者Dragon