WCF自托管服务POST请求CORS错误排查求助

我开发了一个WCF自托管服务，用于与本地连接的打印机通信以打印工牌。浏览器端应用调用该本地服务执行打印操作，所有GET请求均可正常运行，但POST请求始终触发CORS错误，且预请求（Pre-Flight）状态正常。

请求情况说明 #

GET请求（运行正常） #

POST请求（触发CORS错误，预请求正常） #

相关C#代码 #

服务启动代码 #

private void startService_HTTPS(System.Diagnostics.EventLog eventLog)
{
    eventLog.WriteEntry("Begin startService.......");
    string serviceUrl = Config.protocol_https + "://" + Config.host + ":" + Config.portNumber_https;
    WebServiceHost webServiceHost = new WebServiceHost(typeof(Service), new Uri(serviceUrl));
    try
    {
        ServicePointManager.SecurityProtocol = ServicePointManager.SecurityProtocol | SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
    
        KeyedByTypeCollection<IServiceBehavior> behaviors = webServiceHost.Description.Behaviors;
        ServiceMetadataBehavior serviceMetadataBehavior = new ServiceMetadataBehavior()
        {
            HttpGetEnabled = false,
            HttpsGetEnabled = true
            
        };
        behaviors.Add(serviceMetadataBehavior);
        ServiceDebugBehavior serviceDebugBehavior = webServiceHost.Description.Behaviors.Find<ServiceDebugBehavior>();
        if (serviceDebugBehavior == null)
        {
            webServiceHost.Description.Behaviors.Add(new ServiceDebugBehavior()
            {
                IncludeExceptionDetailInFaults = true
            });
        }
        else
        {
            serviceDebugBehavior.IncludeExceptionDetailInFaults = true;
        }
        WebHttpBinding webHttpBinding = new WebHttpBinding(WebHttpSecurityMode.Transport)
        {
            HostNameComparisonMode = HostNameComparisonMode.Exact,
            MaxReceivedMessageSize = (long)2147483647,
            TransferMode = TransferMode.Streamed,
           // CrossDomainScriptAccessEnabled = true
        };
        ServiceEndpoint serviceEndpoint = webServiceHost.AddServiceEndpoint(typeof(IService), webHttpBinding, serviceUrl);
        serviceEndpoint.Behaviors.Add(new WebHttpBehavior());
          serviceEndpoint.Behaviors.Add(new EnableCrossOriginResourceSharingBehavior());

      
        webServiceHost.Open();
        eventLog.WriteEntry("Started HTTPS services successfully......"+serviceUrl);

      //  CertManager certs = new CertManager();
       // certs.setupCerts(eventLog);
        
    }
    catch (CommunicationException cex)
    {
        Console.WriteLine("An exception occurred: {0}", cex.Message);
        eventLog.WriteEntry("Exception "+cex.Message);
        eventLog.WriteEntry(cex.StackTrace);
        webServiceHost.Abort();
    }
}

自定义CORS行为代码 #

public class EnableCrossOriginResourceSharingBehavior : BehaviorExtensionElement, IEndpointBehavior
{
    public void AddBindingParameters(ServiceEndpoint endpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
    {

    }

    public void ApplyClientBehavior(ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.ClientRuntime clientRuntime)
    {

    }

    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.EndpointDispatcher endpointDispatcher)
    {
        var requiredHeaders = new Dictionary<string, string>();

        requiredHeaders.Add("Access-Control-Allow-Origin", "*");
        requiredHeaders.Add("Access-Control-Request-Method", "POST,GET,PUT,DELETE,OPTIONS");
        requiredHeaders.Add("Access-Control-Allow-Headers", "X-Requested-With,Content-Type");

        endpointDispatcher.DispatchRuntime.MessageInspectors.Add(new CustomHeaderMessageInspector(requiredHeaders));
    }

    public void Validate(ServiceEndpoint endpoint)
    {

    }

    public override Type BehaviorType
    {
        get { return typeof(EnableCrossOriginResourceSharingBehavior); }
    }

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

自定义消息检查器代码 #

public class CustomHeaderMessageInspector : IDispatchMessageInspector
{
    private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

    Dictionary<string, string> requiredHeaders;
    public CustomHeaderMessageInspector(Dictionary<string, string> headers)
    {
        requiredHeaders = headers ?? new Dictionary<string, string>();
    }

    public object AfterReceiveRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel, System.ServiceModel.InstanceContext instanceContext)
    {
        return null;
    }

    public void BeforeSendReply(ref System.ServiceModel.Channels.Message reply, object correlationState)
    {
        var httpHeader = reply.Properties["httpResponse"] as System.ServiceModel.Channels.HttpResponseMessageProperty;
        httpHeader.StatusCode = System.Net.HttpStatusCode.OK;

        foreach (var item in requiredHeaders)
        {
            log.Debug("BeforeSendReply add header " + item.Key + ", val " + item.Value);

            httpHeader.Headers.Add(item.Key, item.Value);
        }
    }
}

我已尝试为服务添加自定义CORS行为，但问题仍未解决，在此寻求技术帮助以排查并解决该问题。

内容的提问来源于stack exchange，提问作者user2872741