WF instance learning notes: (2) using workflow to call WCF data services to obtain data

Effect of running the program homepage:

First open the homecontroller. CS File

        public ActionResult Index()        {            #region XAML            //var activity =            //    ActivityXamlServices.Load(            //    Server.MapPath("~/workflows/GetDataForMainPage.xaml"));            //var results = WorkflowInvoker.Invoke(activity);            #endregion            var results =                WorkflowInvoker.Invoke(                new CustomActivities.GetDataForMainPage());            ViewData["candidates"] = results["candidates"];            ViewData["workOrders"] = results["workOrders"];            return View();        }

The program uses workflowinvoker. invoke to call the getdataformainpage activity and save the returned results in viewdata.
Analyze the getdataformainpage Activity

A parallel workflow contains two getodata activities. The returned results of a generic activity, ienumerable <jobcandidate> and ienumerable <workorder>, are bound to the output parameters candidate and workorders.

Next, let's look at the implementation of getodata.

    public sealed class GetOData<T> : AsyncCodeActivity<IEnumerable<T>>    {        [RequiredArgument]        public InArgument<Uri> ServiceUrl { get; set; }        public InArgument<string> EntitySetName { get; set; }        protected override IAsyncResult BeginExecute(AsyncCodeActivityContext context,             AsyncCallback callback, object state)        {             DataServiceContext ctx =                new DataServiceContext(ServiceUrl.Get(context));           DataServiceQuery<T> query = ctx.CreateQuery<T>(EntitySetName.Get(context));           context.UserState = query;           return query.BeginExecute(callback, state);        }        protected override IEnumerable<T> EndExecute(AsyncCodeActivityContext context, IAsyncResult result)        {            DataServiceQuery<T> query = context.UserState as DataServiceQuery<T>;            return query.EndExecute(result);        }            }

The code in this section calls WCF data services through asynchronous dataservicequery.