Resumé

WCF DataServices in Windows Phone 7

Cristian Merighi (Wednesday, August 24, 2011)

Sample code about how to manage a DataContext the asynchronous way.

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How to manage a WCF DataService in Windows Phone 7 (I may write Silverlight)?
Quite simple task, neither a particularly original subject. I just write this article to fix on "paper" the key code needed to accomplish it so that I can retrieve it with relative ease in the future.
(Syntax in the WPF world is almost identical).

    Reading data (C#):

// DataContext proxy instance:
var proxy = new ToolSpare.ToolSpareContext(new Uri("http://myserver/mydataservice.svc/"));
// Build up a query to be executed (cast it as a 
    System.Data.Services.Client.DataServiceQuery) then...
var query = proxy.MovementSet.Where(m => !m.IsIncome).OrderByDescending(m => m.Amount).Take(20) as DataServiceQuery<ToolSpare.Movement>;
// ...execute it asynchronously
query.BeginExecute((asyncResult) =>
{
    // use state token to get the results:
    var state = asyncResult.AsyncState as 
        DataServiceQuery<ToolSpare.Movement>;
    var list = state.EndExecute(asyncResult).ToList();
    list.ForEach(outcome => Dispatcher.BeginInvoke(() =>
    {
        // populate some collection in the ViewModel (execute this code in the UI Thread)
        var item = new ItemViewModel { LineOne = outcome.Amount.ToString("c2"), LineTwo = outcome.Caption, LineThree = string.Format("{0:D} {0:t}", outcome.Date) };
        this.Items.Add(item);
    }));
}, /* state -> */query);

Reading data, alternative way (C#):

// using System.Data.Services.Client.DataServiceCollection
DataServiceCollection<ToolSpare.Movement> outcomes = new DataServiceCollection<ToolSpare.Movement>(proxy);
outcomes.LoadCompleted += (s, e) => // inline delegate, do not try this at home! Always detach handlers :)
{   
    // ensure execution in the UI-Thread;
    foreach (var outcome in outcomes)
    {
        var item = new ItemViewModel { LineOne = outcome.Amount.ToString("c2"), LineTwo = outcome.Caption, LineThree = string.Format("{0:D} {0:t}", outcome.Date) };
        this.Items.Add(item);
    }
};
outcomes.LoadAsync(/* query from above -> */query);

    Saving data (C#):

// changes have been made to the model, DataContext.UpdateObject(...)
proxy.BeginSaveChanges((asyncResult) 
    => this.Dispatcher.BeginInvoke(()=>
{
    // execute code in the UI Thread...
    var ctx = asyncResult.AsyncState as ToolSpare.ToolSpareContext;
    ctx.EndSaveChanges(asyncResult);
    // do something else...
}, null), /* state -> */proxy);