如何将Windows Workflow作为Web服务(.svc)托管？

using System;
using System.ServiceModel.Activities;
using System.Activities;
using System.ServiceModel;
using System.Activities.Statements;

namespace DemoWF
{
    public class _25_LeaveRequest
    {
        public WorkflowService GetInstance()
        {
            WorkflowService service;
            Variable<int> empID = new Variable<int> { Name = "empID" };
            Variable<int> requestID = new Variable<int> { Name = "requestID" };

        Receive receiveLeaveRequest = new Receive
        {
            ServiceContractName = "ILeaveRequestService",OperationName = "ApplyLeave",CanCreateInstance = true,Content = new ReceiveParametersContent
            {
                Parameters ={
                    {"empID",new OutArgument<int>(empID)}
                }
            }
        };

        SendReply replyLeaveRequestID = new SendReply
        {
            Request = receiveLeaveRequest,Content = new SendParametersContent
            {
                Parameters ={
                            {"requestID",new InArgument<int>(requestID)},},};


        Sequence workflow = new Sequence()
        {
            Variables = { empID,requestID },Activities = {
                new WriteLine{Text="WF service is starting..."},receiveLeaveRequest,new WriteLine{
                    Text=new InArgument<string>(aec=> "Emp ID="+empID.Get(aec).ToString())
                },new Assign<int>{
                    Value=new InArgument<int>(5),To=new OutArgument<int>(requestID)
                },new WriteLine{
                    Text=new InArgument<string>(aec=> "Request ID="+requestID.Get(aec).ToString())
                },replyLeaveRequestID
            },};

        service = new WorkflowService
        {
            Name = "AddService",Body = workflow
        };
        return service;
    }
}

现在,它是自我托管的,如下所示

namespace DemoWF
{
    class Program
    {
        static void Main(string[] args)
        {
            LeaveRequest();
        }

        private static void LeaveRequest()
        {
            _25_LeaveRequest receiveAndReplyWorkflow = new _25_LeaveRequest();
            WorkflowService wfService = receiveAndReplyWorkflow.GetInstance();
            Uri address = new Uri("http://localhost:8000/WFServices");
            WorkflowServiceHost host = new WorkflowServiceHost(wfService,address);

            try
            {
                Console.WriteLine("Opening Service...");
                host.Open();

                Console.WriteLine("WF service is listening on " + address.ToString() + ",press any key to close");
                Console.ReadLine();
            }
            catch (Exception e)
            {
                Console.WriteLine("some thing bad happened" + e.StackTrace);
            }
            finally
            {
                host.Close();
            }
        }
    }
}