Danny Garber's Web Blog

Follow up on my previous blog on how to use the asynchronous methods of the Live Mesh in the Live Framework April 2009 CTP, I have received the comment from my colleague Ben Williams, who rightfully pointed out that with use of CreateQuery<T>() method of Mesh Application Service object, I could have accomplished the task of adding a new Data Feed in just two event handler steps comparing to the four steps shown in my previous post. Here is the new and updated snippet code that demonstrates the technique used to add a new Data Feed object into the Live Mesh:

        public void DataFeeds_Create(Claim claim)

        {

            this.claim = claim;

            DataFeed claimFeed = new DataFeed(claim.RefNumber);

            MeshApplicationService meshApp = Application.Current.GetMeshApplicationService();

            meshApp.DataFeeds.AddCompleted += new EventHandler<LiveItemEventArgs<DataFeed>>(DataFeeds_AddCompleted);

            meshApp.DataFeeds.AddAsync(claimFeed, claim.RefNumber);

        }

        public void DataFeeds_AddCompleted(object sender, LiveItemEventArgs<DataFeed> e)

        {

            MeshApplicationService meshApp = Application.Current.GetMeshApplicationService();

            var query = from datafeed in meshApp.CreateQuery<DataFeed>()

                        where datafeed.Resource.Title == (string)e.UserState

                        select datafeed;

            //Get a the DataFeed

            DataFeed claimFeed = query.FirstOrDefault();

            claimFeed = (DataFeed)meshApp.CreateQuery<DataFeed>().Where(d => d.Resource.Title == (string)e.UserState)

                                        .Single();

            //then add a new DataEntry

            DataEntryResource entryResource = new DataEntryResource();

            entryResource.Type = "Claim";

            DataEntry claimEntry = new DataEntry(entryResource);

            //Set the user data

            claimEntry.Resource.SetUserData<string>(claim.WriteToXml().ToString(System.Xml.Linq.SaveOptions.None));

            //Add DataEntry to the DataEntries collection

            claimFeed.DataEntries.AddCompleted += new EventHandler<LiveItemEventArgs<DataEntry>>(DataEntries_AddCompleted);

            claimFeed.DataEntries.AddAsync(claimEntry, claimFeed);

        }

Well, with recent release of the Live Framework April 2009 CTP, we've got a bunch of new functionality and support, along with a long list of "legacy" methods and classes being depreciated. To find more details on what new features have been added and what classes and methods have been removed, see this post: http://blogs.msdn.com/liveframework/archive/2009/03/11/live-framework-updated.aspx

The main change I found in this new CTP release, is that all sync roundtrip calls to the Live Mesh server have been replaced with asynchronous methods. For instance, instead of using DataFeeds.Add() method to add a new Data Feed object, now you have to use a sequence of asynchronous calls and in the correct order. Being mostly on my own facing this new challenge (it is needless to say that after I redirected my project to reference the new Live Framework assemblies, my project build was broken), I spent about 2 days to figure out the correct sequence and the right methods to call when adding a new Data Feed Entry object into my Live Mesh. Below, is the snippets of the sequence calls you must perform in order to achieve the same objective you saw earlier in this post.

In the Live Framework April 2009 CTP:

1.      Step 1: Add DataFeed to the DataFeeds collection

       MeshApplicationService meshApp = Application.Current.GetMeshApplicationService();

       DataFeed claimFeed = new DataFeed(claim.RefNumber);

       meshApp.DataFeeds.AddCompleted +=new EventHandler<LiveItemEventArgs<DataFeed>>(DataFeeds_AddCompleted);

       meshApp.DataFeeds.AddAsync(claimFeed, claimFeed);

2.      Step 2:  Load DataFeeds (upon DataFeeds_AddCompleted() event handler call)

       MeshApplicationService meshApp = Application.Current.GetMeshApplicationService();

       meshApp.DataFeeds.LoadCompleted += new EventHandler<System.ComponentModel.AsyncCompletedEventArgs>(DataFeeds_LoadCompleted);

       meshApp.DataFeeds.LoadAsync(e.UserState);

3.      Step 3: Load a newly added DataFeed (upon DataFeeds_LoadCompleted() event hander call)

       DataFeed claimFeed = (DataFeed)e.UserState;

       claimFeed.LoadCompleted += new EventHandler<System.ComponentModel.AsyncCompletedEventArgs>(claimFeed_LoadCompleted);

       claimFeed.LoadAsync(claim.RefNumber);

4.      Step 4: Get loaded DataFeed and add a new DataEntry to its DataEntries collection (upon claimFeed_LoadCompleted() event handler call)

       MeshApplicationService meshApp = Application.Current.GetMeshApplicationService();

       //Verify that the new DataFeed object is loaded

       int count = meshApp.DataFeeds.Entries.Where(f => f.Resource.Title == e.UserState.ToString()).Count();

       if (count <> 1) throw new Exception(String.Format("Found {0} identical Data Entries", count));

       //Get a new DataFeed

       DataFeed claimFeed = meshApp.DataFeeds.Entries.Where(f => f.Resource.Title == e.UserState.ToString()).Single();

       //then add a new DataEntry

       DataEntryResource entryResource = new DataEntryResource();

       entryResource.Type = "Claim";

       DataEntry claimEntry = new DataEntry(entryResource);

       //Set the user data

       claimEntry.Resource.SetUserData<string>(claim.WriteToXml().ToString(System.Xml.Linq.SaveOptions.None));

       //Add DataEntry to the DataEntries collection

       claimFeed.DataEntries.AddCompleted +=new EventHandler<LiveItemEventArgs<DataEntry>>(DataEntries_AddCompleted);

       claimFeed.DataEntries.AddAsync(claimEntry, claimFeed);