WCF host to add custom HTTP header to response

Question

I have a standalone C# WCF service running as a Windows service. I have the requirement to add custom headers like X-Frame-Options to all responses. I have tried to add an instance of the following class to ServiceEndpoint.Behaviors

internal class ServerInterceptor : IDispatchMessageInspector, IEndpointBehavior
{
    object IDispatchMessageInspector.AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
    {
        return null;
    }

    void IDispatchMessageInspector.BeforeSendReply(ref Message reply, object correlationState)
    {
        reply.Properties.Add("X-Frame-Options", "deny");
    }

    void IEndpointBehavior.ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {
        endpointDispatcher.DispatchRuntime.MessageInspectors.Add(this);
    }

    void IEndpointBehavior.Validate(ServiceEndpoint endpoint) { }

    void IEndpointBehavior.AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters) { }

    void IEndpointBehavior.ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime) { }
}

This doesn't add any HTTP header to the response although the class gets called as the debugger can step into the BeforeSendReply function. Furthermore if I replace reply.Properties with reply.Headers then the header is added, but not to the HTTP headers but to the SOAP headers.

How can I add a HTTP header like X-Frame-Options to the response?

Dİd you try HttpRequestMessageProperty requestMessage = new HttpRequestMessageProperty(); requestMessage.Headers["X-Frame-Options"] = "deny"; OperationContext.Current.OutgoingMessageProperties[HttpRequestMessageProperty.Name] = requestMessage;? — Selim Yildiz
– Selim Yildiz, Commented Mar 11, 2020 at 5:24
I also found this code snippet and it doesn't work (cannot work, to be exact), as there's no "X-Frame-Options" header. — Daniel
– Daniel, Commented Mar 11, 2020 at 8:18

Abraham Qian · Accepted Answer · 2020-03-11 09:12:17Z

1

I made an example, which is used to add extra CORS HTTP header, wish it is instrumental for you.
Message Inspector.

        public class CustomHeaderMessageInspector : IDispatchMessageInspector
        {
            Dictionary<string, string> requiredHeaders;
            public CustomHeaderMessageInspector(Dictionary<string, string> headers)
            {
                requiredHeaders = headers ?? new Dictionary<string, string>();
            }
            public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
            {
                string displayText = $"Server has received the following message:\n{request}\n";
                Console.WriteLine(displayText);
                return null;
            }

            public void BeforeSendReply(ref Message reply, object correlationState)
            {
                if (!reply.Properties.ContainsKey("httpResponse")) 
                reply.Properties.Add("httpResponse", new HttpResponseMessageProperty());

                var httpHeader = reply.Properties["httpResponse"] as HttpResponseMessageProperty;
                foreach (var item in requiredHeaders)
                {
                    httpHeader.Headers.Add(item.Key, item.Value);
                }

                string displayText = $"Server has replied the following message:\n{reply}\n";
                Console.WriteLine(displayText);

            }
    }

Custom Contract Attribute.

public class MyBehaviorAttribute : Attribute, IContractBehavior, IContractBehaviorAttribute
    {
        public Type TargetContract => typeof(MyBehaviorAttribute);

        public void AddBindingParameters(ContractDescription contractDescription, ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
        {
        }

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

        public void ApplyDispatchBehavior(ContractDescription contractDescription, ServiceEndpoint endpoint, DispatchRuntime dispatchRuntime)
        {
            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");

            dispatchRuntime.MessageInspectors.Add(new CustomHeaderMessageInspector(requiredHeaders));
        }

        public void Validate(ContractDescription contractDescription, ServiceEndpoint endpoint)
        {

        }
}

Apply the contract behavior.

[ServiceContract(Namespace = "mydomain")]
[MyBehavior]
public interface IService
{
    [OperationContract]
    [WebGet]
    string SayHello();
}

Result.

Feel free to let me know if there is anything I can help with.

edited Mar 11, 2020 at 9:12

answered Mar 11, 2020 at 7:03

Abraham Qian

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3 Comments

Daniel Over a year ago

Thanks but the line var httpHeader = reply.Properties["httpResponse"] as HttpResponseMessageProperty; throws this exception: System.ServiceModel.FaultException`1[System.ServiceModel.ExceptionDetail]: A property with the name 'httpResponse' is not present.

Daniel Over a year ago

If you modify your code and add

if (!reply.Properties.ContainsKey("httpResponse"))                 reply.Properties.Add("httpResponse", new HttpResponseMessageProperty());

to the beginning of BeforeSendReply() then I'll accept your answer.

Abraham Qian Over a year ago

My bad. I forget the binding type used in WCF, if the WCF isn’t created by Webhttpbinding, we should add your code segment. It will work perfectly. I have updated it.

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