Using Rx in Silverlight for WCF Calls Doesn't Work with TakeUntil

Question

I have the following bit of code to configure my Rx connections:

Event Definitions:

    public class QueryEventArgs : EventArgs
    {
        public SomeParametersType SomeParameters
        {
            get;
            set;
        }

        public object QueryContext
        {
                     get;
            set;
        }
    };

    public delegate void QueryDelegate(object sender, QueryEventArgs e);

    public event QueryDelegate QueryEvent;

Initialization:

            queryObservable = Observable.FromEvent<QueryEventArgs>(this, "QueryEvent");
            queryObservable.Subscribe((e) =>
            {
                tbQueryProgress.Text = "Querying... ";
                client.QueryAsync(e.EventArgs.SomeParameters, e.EventArgs.QueryContext);
            });

            queryCompletedObservable = from e in Observable.FromEvent<QueryCompletedEventArgs>(client, "QueryCompleted").TakeUntil(queryObservable) select e;

            queryCompletedObservable.Subscribe((e) =>
                {
                    tbQueryProgress.Text = "Ready";
                    SilverlightClientService_QueryCompleted(e.Sender, e.EventArgs);
                },
                (Exception ex) =>
                {
                    SetError("Query error: " + ex);
                }
            );

the "client" is a WCF client, and everything else is pretty clear.

"TakeUntil" is designed so that the user does not rush himself when performing a new request, being in the middle of the current one. However, although the code works, if I delete the TakeUntil clause, if I insert it, the request will never be completed.

Is this the correct template? If so, am I doing something wrong?

Cheers, -Tim

Answer 1

TakeUntil , , queryObservable , .

IObservable , Switch, , .

public static class ClientExtensions
{
    public static IObservable<QueryCompletedEventArgs> QueryObservable(
        this QueryClient client,
        object[] someParameters, object queryContext)
    {
       return Observable.CreateWithDisposable<QueryCompletedEventArgs>(observer =>
       {
            var subscription = Observable.FromEvent<QueryCompletedEventArgs>(
                    h => client.QueryCompleted += h,
                    h => client.QueryCompleted -= h
                )
                .Subscribe(observer);

            client.QueryAsync(someParameters, queryContext);

            return new CompositeDisposable(
                subscription,
                Disposable.Create(() => client.Abort())
            );
        });
    }
}

:

queryObservable = Observable.FromEvent<QueryEventArgs>(this, "QueryEvent");

queryObservable
    .Select(query => client.QueryObservable(
        query.EventArgs.SomeParameters, 
        query.EventArgs.QueryContext
    ))
    .Switch()
    .Subscribe(queryComplete =>
    {
        tbQueryProgress.Text = "Ready";
        // ... etc
    });

, "" , . ( ) .