Windows Workflow Foundation ASP.NET State Machine

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Workflow.Runtime;
using System.Workflow.Runtime.Hosting;
using System.Web.Caching;
using System.Collections.Specialized;
using System.IO;
using System.Workflow.Activities;
using System.Web.Configuration;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;

namespace JQD
{
    /// <summary>
    ///  This is modified from Jon Flanders' Blog ASPNET Workflow example.
    ///  Local and ManualScheduler services are attached to Workflow runtime.
    /// </summary>
    public class WorkflowHost : IHttpModule
    {
        static object _sync = new object();
        static string _WFName = "WorkflowRuntimeWithServices";

        #region Build a runtime with Services and cache it

        public static WorkflowRuntime RuntimeWithServices
        {
            get
            {
                object owr = HttpContext.Current.Cache[_WFName]; // Cache is per AppDomain
                WorkflowRuntime wr = null;
                if (owr == null)
                {
                    lock (_sync)
                    {
                        // need to check again since another thread could have just created 
                        // one WF runtime while this thread is waiting for the lock
                        owr = HttpContext.Current.Cache[_WFName]; 
                        if (owr == null)   
                        {
                            wr = new WorkflowRuntime();
                            wr.AddService(new ManualWorkflowSchedulerService());
                            ExternalDataExchangeService de = new ExternalDataExchangeService();
                            wr.AddService(de);
                            de.AddService(new JQD.LocalService());  // each solution need to change this !!!
                            wr.StartRuntime();
                            HttpContext.Current.Cache.Add(_WFName, wr, null, Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration, CacheItemPriority.NotRemovable, null);
                        }
                        else
                            wr = owr as WorkflowRuntime;
                    }
                }
                else
                    wr = owr as WorkflowRuntime;
                return wr;
            }
        }

        #endregion

        #region other code for Http Module

        public void Dispose() { }
        public void Init(HttpApplication app)
        {
            app.BeginRequest += new EventHandler(app_BeginRequest);
        }
        void app_BeginRequest(object sender, EventArgs e) { }

        #endregion

    }
}