private static IDisposable InvokeTaskWithDisposable <TState>(
IScheduler scheduler,
TState state,
Func <CancellationToken, IScheduler, TState, Task <IDisposable> > taskBuilder,
SchedulerSynchronizationContext schedulerContext)
{
var subscriptions = new SerialDisposable();
var cancellationDisposable = new CancellationDisposable().DisposeWith(subscriptions);
using (SynchronizationContextHelper.ScopedSet(schedulerContext))
{
taskBuilder(cancellationDisposable.Token, scheduler, state)
.ContinueWith(t =>
{
if (t.IsCanceled)
{
subscriptions.Disposable = null;
}
else if (t.IsFaulted)
{
subscriptions.Disposable = scheduler.Schedule(() => { t.Exception.Handle(e => e is OperationCanceledException); });
}
else
{
subscriptions.Disposable = t.Result;
}
}, TaskContinuationOptions.ExecuteSynchronously);
}
return(subscriptions);
}
/// <summary>
/// Schedules work using an asynchronous method, allowing for cooperative scheduling in an imperative coding style.
/// </summary>
/// <param name="scheduler">Scheduler to schedule work on.</param>
/// <param name="state">State to pass to the asynchronous method.</param>
/// <param name="taskBuilder">Asynchronous method to run the work.</param>
/// <returns>Disposable object that allows to cancel outstanding work on cooperative cancellation points or through the cancellation token passed to the asynchronous method.</returns>
public static IDisposable ScheduleTask <TState>(
this IScheduler scheduler, TState state,
Func <CancellationToken, IScheduler, TState, Task> taskBuilder)
{
var schedulerContext = new SchedulerSynchronizationContext(scheduler);
return(scheduler.Schedule(state, (s, st) => InvokeTask(scheduler, st, taskBuilder, schedulerContext)));
}
/// <summary>
/// Schedulers the specified task on the specified scheduler.
/// </summary>
/// <param name="source"></param>
/// <param name="taskBuilder"></param>
/// <returns></returns>
public static IDisposable Schedule(this IScheduler source, Func <CancellationToken, Task> taskBuilder)
{
var subscriptions = new CompositeDisposable(2);
var cancellationDisposable = new CancellationDisposable();
// Capture the source context before calling schedule.
var sourceCtx = new SchedulerSynchronizationContext(source);
// It is acceptable to use the async void pattern as long as the
// synchronization context is not the default, i.e. executing on the thread pool,
// where exceptions are not trapped properly.
System.Reactive.Concurrency.Scheduler.Schedule(
source,
() =>
{
using (SynchronizationContextHelper.ScopedSet(sourceCtx))
{
taskBuilder(cancellationDisposable.Token)
.ContinueWith(t =>
{
if (t.IsFaulted)
{
source.Schedule(() =>
{
throw t.Exception;
});
}
}
);
}
}
).DisposeWith(subscriptions);
cancellationDisposable.DisposeWith(subscriptions);
return(subscriptions);
}