Question

I want to create a DispatchMessageInspector for my WCF service that will run before each operation, perform some processing and then make the result of that processing available to the operation.

Creating the MessageInspector is easy. However, after I do what I need to do there, where can I place the object that I create so it can be accessed by the code in each operation? In the MessageInspector, would I just store it in the OperationConext, or is there a cleaner solution?

Answer 1

You’d normally store this information on the message properties, then access it via the operation context on the operation (see an example in the code below).

public class StackOverflow_7534084
{
    const string MyPropertyName = "MyProp";
    [ServiceContract]
    public interface ITest
    {
        [OperationContract]
        string Echo(string text);
    }
    public class Service : ITest
    {
        public string Echo(string text)
        {
            Console.WriteLine("Information from the inspector: {0}", OperationContext.Current.IncomingMessageProperties[MyPropertyName]);
            return text;
        }
    }
    public class MyInspector : IEndpointBehavior, IDispatchMessageInspector
    {
        public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
        {
        }

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

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

        public void Validate(ServiceEndpoint endpoint)
        {
        }

        public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
        {
            request.Properties[MyPropertyName] = "Something from the inspector";
            return null;
        }

        public void BeforeSendReply(ref Message reply, object correlationState)
        {
        }
    }
    public static void Test()
    {
        string baseAddress = "http://" + Environment.MachineName + ":8000/Service";
        ServiceHost host = new ServiceHost(typeof(Service), new Uri(baseAddress));
        host.AddServiceEndpoint(typeof(ITest), new BasicHttpBinding(), "").Behaviors.Add(new MyInspector());
        host.Open();
        Console.WriteLine("Host opened");

        ChannelFactory<ITest> factory = new ChannelFactory<ITest>(new BasicHttpBinding(), new EndpointAddress(baseAddress));
        ITest proxy = factory.CreateChannel();
        Console.WriteLine(proxy.Echo("Hello"));

        ((IClientChannel)proxy).Close();
        factory.Close();

        Console.Write("Press ENTER to close the host");
        Console.ReadLine();
        host.Close();
    }
}