Asynchronous equivalent of .NET's System.Action and System.Action<T> using UniTask for Unity

ActionAsync.cs

public delegate UniTask ActionAsync(CancellationToken cancellationToken);

public delegate UniTask ActionAsync<in T>(T value, CancellationToken cancellationToken);

public static class ActionAsyncExtensions
{
    public static UniTask InvokeAsync(this ActionAsync handler, CancellationToken cancellationToken)
    {
        Delegate[] delegates = handler?.GetInvocationList();

        if (delegates == null || delegates.Length == 0)
            return UniTask.CompletedTask;

        var tasks = new UniTask[delegates.Length];

        for (var i = 0; i < delegates.Length; i++)
            tasks[i] = (UniTask) delegates[i].DynamicInvoke(cancellationToken);

        return UniTask.WhenAll(tasks);
    }
    
    public static UniTask InvokeAsync<T>(this ActionAsync<T> handler, T value, CancellationToken cancellationToken)
    {
        Delegate[] delegates = handler?.GetInvocationList();

        if (delegates == null || delegates.Length == 0)
            return UniTask.CompletedTask;

        var tasks = new UniTask[delegates.Length];

        for (var i = 0; i < delegates.Length; i++)
            tasks[i] = (UniTask) delegates[i].DynamicInvoke(value, cancellationToken);

        return UniTask.WhenAll(tasks);
    }
}

Example.cs

public class Door : MonoBehaviour
{
    public event ActionAsync OnOpening;
    public event Action OnOpened;
    
    public event ActionAsync OnClosing;
    public event Action OnClosed;

    public async UniTask OpenDoor(CancellationToken cancellationToken)
    {
        await OnOpening.InvokeAsync(cancellationToken);
        OnOpened?.Invoke();
    }
    
    public async UniTask CloseDoor(CancellationToken cancellationToken)
    {
        await OnClosing.InvokeAsync(cancellationToken);
        OnClosed?.Invoke();
    }
}

public class DoorAnimationBehaviour : MonoBehaviour
{
    [SerializeField]
    private Door door;

    [SerializeField]
    private Animator doorAnimator;

    private void OnEnable()
    {
        door.OnOpening += AnimateDoorOpening;
        door.OnClosing += AnimateDoorClosing;
    }

    private void OnDisable()
    {
        door.OnOpening -= AnimateDoorOpening;
        door.OnClosing -= AnimateDoorClosing;
    }

    private async UniTask AnimateDoorOpening(CancellationToken cancellationToken)
    {
        doorAnimator.SetBool("IsOpen", true);
        await UniTask.WaitWhile(() => doorAnimator.GetCurrentAnimatorStateInfo(0).IsName("Opening"), PlayerLoopTiming.Update, cancellationToken);
    }
    
    private async UniTask AnimateDoorClosing(CancellationToken cancellationToken)
    {
        doorAnimator.SetBool("IsOpen", false);
        await UniTask.WaitWhile(() => doorAnimator.GetCurrentAnimatorStateInfo(0).IsName("Closing"), PlayerLoopTiming.Update, cancellationToken);
    }
}