public IObservable <T> Use <T>(Func <IDatabaseConnection, CancellationToken, IEnumerable <T> > f)
{
Contract.Requires(f != null);
if (disposed)
{
throw new ObjectDisposedException(this.GetType().FullName);
}
return(Observable.Create((IObserver <T> observer, CancellationToken cancellationToken) =>
{
// Prevent calls to subscribe after the connection is disposed
if (this.disposed)
{
observer.OnError(new ObjectDisposedException(this.GetType().FullName));
return Task.FromResult(Unit.Default);
}
return queue.EnqueueOperation(ct =>
{
this.progressHandlerResult.Value = false;
var ctSubscription = ct.Register(() => this.progressHandlerResult.Value = true);
try
{
ct.ThrowIfCancellationRequested();
// Note: Diposing the connection wrapper doesn't dispose the underlying connection
// The intent here is to prevent access to the underlying connection outside of the
// function call.
using (var db = new DelegatingDatabaseConnection(this.conn))
{
foreach (var e in f(db, ct))
{
observer.OnNext(e);
ct.ThrowIfCancellationRequested();
}
observer.OnCompleted();
}
}
finally
{
ctSubscription.Dispose();
this.progressHandlerResult.Value = false;
}
}, scheduler, cancellationToken);
}));
}
public static Task EnqueueOperation(this OperationsQueue This, Action <CancellationToken> calculationFunc, IScheduler scheduler, CancellationToken cancellationToken) =>
This.EnqueueOperation(ct =>
Observable.Start(() => calculationFunc(ct), scheduler).ToTask(),
cancellationToken);