This will be a longish post .. you have been warned 🙂

I think OData is rather cool .. head over (here) to learn more, if you haven’t already. There is nothing proprietary  about it; just culmination of existing technologies of HTTP, AtomPub and Json to provide a platform independent way of sharing information. As I heard someone say “..think of it as RSS for real updateable data..” and in this new age of www as a collection of connected web services rather than collection of web pages, I think OData can play an important role. Why the restrictions against opening up our data to interoperability if we can put adequate security on it?

Now, I wanted to talk about OData from a Windows Phone standpoint (specially WP7.5 or Mango); but also something that applies equally & is just as easily doable on other mobile OS platforms. Most well-designed mobile solutions these days also have a web interface that allows for easier data entry than on a phone form factor; yet data has to stay in sync whenever the user switches between platforms. A centralized data repository with OData feeds seems perfect for a case like this .. so, that’s what we shall talk about in this post.

After looking around a little bit on OData & WP7, I found a lot of examples on how to set up an OData source & consume the feeds from a Windows Phone app. This is obviously the first step & rather important as we shall see; but I also wanted to see if I could set up CRUD operations from WP7 back to the OData source. In the meantime, check out these few posts on how to consume OData in the first place:

• Surely, one of the best ways to play with OData in real world is the Netflix catalog. Netflix worked with MSFT to expose their entire data set through an OData service (here) and now it becomes easy for various applications to consume the vast information in their catalog. This series of posts (here) covers how to build a Windows Phone client to browse through the Netflix catalog.

• Michael Crump did this brilliant series on how to set up an OData source & consume it in Silverlight/Windows Phone. You may find it (here).

• Post (here) from your’s truly on how to consume OData feeds from SQL Azure in a Windows Phone app.

SQL Azure Team Table

WCF Service in Azure

Now, let’s switch focus to our Windows Phone app. We can obviously read data out of the Azure OData feed pretty easily, as evident (here). What we want to be trying to do is to add records into the SQL Azure table from the Windows Phone app. Accordingly, we add a little UI for allowing data entry; end goal is something like this:

Team in WP7

Added Team Member through WP7

The way we go about doing this is by adding a Reference to our own WCF Service hosted in Azure, as below. Please note, that this will work only in Windows Phone 7.1 Mango tooling:

Add WCF Service Ref.

With the service reference under our belt, we now have a direct context of the OData service in Azure. Accordingly, we can have access to “Team ” collection objects in code & be able to manipulate them at will. In our case, we already have Sam & Jeff in the SQL Azure table; we want the phone app to add a new member Mike. Here’s some code:

using Demo;
using System.Data.Services.Client;

namespace SQLAzureOData_Demo
{
    using DemoService;

    public partial class MainPage : PhoneApplicationPage
    {
       private static DemoEntities wcfContext = null;

       private void InsertDataThruService()
        {
            wcfContext = new DemoEntities(new Uri("http://YourAzureServiceNDS.cloudapp.net/DemoService.svc/"));

            var TeamMember = Team.CreateTeam(3);
            TeamMember.Name = "Mike";
            TeamMember.TwitterHandle = "@michaelcollier";

            var collection = new DataServiceCollection(wcfContext);
            collection.Add(TeamMember);
            wcfContext.BeginSaveChanges(new AsyncCallback(SaveChangesCB), null);
        }

        private void SaveChangesCB(IAsyncResult asynchronousResult)
        {
            // Warning: You are on a different thread!
            // Success or Error Handling.
            Dispatcher.BeginInvoke(() =>
                {
                    MessageBox.Show("All done!");
                    LoadTeam();
                });
        }
     }
}

Just a few points to mention. On hitting the “+” App icon, I have a little UI pop-up that accepts the new Team members Name & TwitterHandle. The code sample above hard-codes the user; but you get the point that the UI needs to fire the “InsertDataThruService” method. Once we have the “WCFContext”, you can see how easy it gets to manipulate the data through any CRUD operations. Another important point to keep in mind is that the “BeginSaveChanges” call is asynchronous, this being Silverlight. So, the “SaveChangesCB” callback delegate does not fire on the same UI thread. This is important to keep in mind if you start wondering why the message pop-up or the refresh of the Team member list in our case, does not fire.

That’s it, few steps; but now we have a fully functional data repository that exposes OData feeds and can be read/updated from multiple platforms. This Service Reference way is just one way to do CRUD on an OData service though. In the next post, we talk about how to do this natively.

Hope this was helpful.

Adios!