A helper library for async/await.

Supports .NET 4.5/4.0, iOS, Android, Windows Store 8.0, Windows Phone Silverlight 8.0/7.5, Windows Phone Applications 8.1, Silverlight 5.0/4.0, and all portable libraries thereof.

Note: iOS applications need to add a special line of code to prevent aggresive compiler optimizations:

EnlightenmentVerification.EnsureLoaded();

Install the NuGet package.

A lot of developers start using this library for AsyncLock, an async-compatible mutual exclusion mechanism. Using AsyncLock is straightforward:

private readonly AsyncLock _mutex = new AsyncLock();
public async Task UseLockAsync()
{
  // AsyncLock can be locked asynchronously
  using (await _mutex.LockAsync())
  {
    // It's safe to await while the lock is held
    await Task.Delay(TimeSpan.FromSeconds(1));
  }
}

AsyncLock also fully supports cancellation:

public async Task UseLockAsync()
{
  // Attempt to take the lock only for 2 seconds.
  var cts = new CancellationTokenSource(TimeSpan.FromSeconds(2));
  
  // If the lock isn't available after 2 seconds, this will
  //  raise OperationCanceledException.
  using (await _mutex.LockAsync(cts.Token))
  {
    await Task.Delay(TimeSpan.FromSeconds(1));
  }
}

AsyncLock also has a synchronous API. This permits some threads to acquire the lock asynchronously while other threads acquire the lock synchronously (blocking the thread).

public async Task UseLockAsync()
{
  using (await _mutex.LockAsync())
  {
    await Task.Delay(TimeSpan.FromSeconds(1));
  }
}

public void UseLock()
{
  using (_mutex.Lock())
  {
    Thread.Sleep(TimeSpan.FromSeconds(1));
  }
}

AsyncLock is just the beginning. The AsyncEx library contains a full suite of coordination primitives: AsyncManualResetEvent, AsyncAutoResetEvent, AsyncConditionVariable, AsyncMonitor, AsyncSemaphore, AsyncCountdownEvent, AsyncBarrier, and AsyncReaderWriterLock.

NotifyTaskCompletion is a data-binding-friendly wrapper for a Task, raising property-change notifications when the task completes. PropertyProgress exposes progress updates as property-change events.

There's quite a few other helpful types; see the Wiki for full details

Need strong-naming? Use the assembly strong naming toolkit.