[ServiceContract]
public interface IService
{
    [OperationContract]
    string Invoke(string input);
}

public class Service : IService
{
    public string Invoke(string input)
    {
        return input;
    }
}

public class OperationSelector : IDispatchOperationSelector
{
    public string SelectOperation(ref Message message)
    {
        return "Invoke";
    }
}

public class EndpointBehavior : IEndpointBehavior
{
    public void Validate(ServiceEndpoint endpoint)
    { }

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

    public void ApplyDispatchBehavior(ServiceEndpoint endpoint,
        EndpointDispatcher endpointDispatcher)
    {
        endpointDispatcher.DispatchRuntime.OperationSelector = new OperationSelector();
    }

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

static void Main(string[] args)
{
    var host = new ServiceHost(typeof(Service),
        new Uri("http://localhost:8000/Service.svc"));
    var endpoint = host.AddServiceEndpoint(typeof(IService), new BasicHttpBinding(), "");
    endpoint.Behaviors.Add(new EndpointBehavior());
    host.Open();

    Console.ReadLine();
    host.Close();
}

POST http://localhost:8000/Service.svc HTTP/1.1
Content-Type: text/xml; charset=utf-8
SOAPAction: "http://tempuri.org/IService/Invoke"
Host: localhost:8000
Expect: 100-continue
Accept-Encoding: gzip, deflate
Connection: Keep-Alive
Content-Length: 158

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"><s:Body><Invoke xmlns="http://tempuri.org/"><input>Test</input></Invoke></s:Body></s:Envelope>

[OperationContract(Action = "*")]
void UnrecognizedMessageHandler(Message msg);