MEF and Workflow Services Integration

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.ServiceModel;
using System.ServiceModel.Dispatcher;
using System.Text;
using System.ServiceModel.Description;
using System.ServiceModel.Activities;
using BaseLibrary;
using System.ServiceModel.Channels;

namespace BaseLibrary
{
    public abstract class MefWorkflowProviderExtensionBehavior : IServiceBehavior
    {      
        /// <summary>
        /// Where the magic happens and your extension gets added to the workflow service host
        /// </summary>
        /// <param name="serviceDescription"></param>
        /// <param name="serviceHostBase"></param>
        public void ApplyDispatchBehavior(ServiceDescription serviceDescription, System.ServiceModel.ServiceHostBase serviceHostBase)
        {
            WorkflowServiceHost host = serviceHostBase as WorkflowServiceHost;
            if (host != null)
            {
                // register the mef provider
                host.WorkflowExtensions.Add(GetProvider());

                // register a error handler on the channel dispatchers
                foreach (ChannelDispatcher cd in host.ChannelDispatchers)
                {
                    cd.ErrorHandlers.Add(new WorkflowUnhandledException());
                }
            }
        }

        protected abstract MefWorkflowProvider GetProvider();

        public virtual void AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters) { }
        public virtual void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) { }
    }
}