WCF: Injecting custom headers for an operation through decoration

Hi I need to inject a custom header in the message if the operation is decorated.

What have I done so far? 1) Created an Attribute by inheriting Attribute and IOperationBehavior 2) Attached a custom OperationInvoker with the operation

Attribute:

public class RankAttribute : Attribute, IOperationBehavior
{ 
     public void ApplyDispatchBehavior(OperationDescription operationDescription, DispatchOperation dispatchOperation)
    {
        dispatchOperation.Invoker = new PublishMessageInvoker(dispatchOperation.Invoker);
    }
    //rest of the methods
}

Interface:

public interface INullableService
{
    [OperationContract]
    [FaultContract(typeof(BusinessServiceException))]
    [Rank]
    NullableResponse NullChecking(NullableRequest request);

    [OperationContract]
    [FaultContract(typeof(BusinessServiceException))]
    NullableResponse NullChecking2(NullableRequest request);
}

Now the problem is, I dont know where to modify the message header, I get access to the Message via operationDiscription.Messages[] but the documentation says that any modification will yield unexpected results.

Thanks, Avinash

Solution

never mind :) it was trivial :) .. you get access to OperationContext in IOperationInvoker

public class PublishMessageInvoker : IOperationInvoker
{
    private IOperationInvoker invoker;


    public PublishMessageInvoker(IOperationInvoker invoker)
    {
        logger.Info("PublishMessageInvoker");
        this.invoker = invoker;

    }

    public object[] AllocateInputs()
    {

        if (invoker == null)
            return null;
        return this.invoker.AllocateInputs();
    }

    public object Invoke(object instance, object[] inputs, out object[] outputs)
    {
       OperationContext.Current.OutgoingMessageHeaders.Add(
            MessageHeader.CreateHeader(
                "customheader",
                "asnjnjdhbhb.com",
                "MyAction")
                );
        return this.invoker.Invoke(instance, inputs, out outputs);
    }

    public IAsyncResult InvokeBegin(object instance, object[] inputs, AsyncCallback callback, object state)
    {

        if (invoker == null)
            return null;
        return this.invoker.InvokeBegin(instance, inputs, callback, state);
    }

    public object InvokeEnd(object instance, out object[] outputs, IAsyncResult result)
    {

        if (invoker == null)
        {
            outputs = null;
            return null;
        }
        return this.invoker.InvokeEnd(instance, out outputs, result);
    }

    public bool IsSynchronous
    {
        get {

            if (invoker == null) return true;
            return this.invoker.IsSynchronous; 
        }
    }
}