/// <summary>
/// Asynchronously registers a handler.
/// </summary>
/// <param name="handlerFactory">The handler to register.</param>
/// <returns>A task representing the asynchronous operation.</returns>
/// <exception cref="ArgumentNullException">Thrown if <paramref name="handlerFactory"/> is null.</exception>
public async Task RegisterAsync(IContextualProvider <THandler> handlerFactory)
{
if (handlerFactory == null)
{
throw new ArgumentNullException(nameof(handlerFactory));
}
Debug.Assert(_handlerStack != null);
Debug.Assert(_lock != null);
using (await _lock.LockAsync())
{
if (_handlerStack.IsEmpty)
{
await PushHandler(handlerFactory);
await _dispatchForwarding.RegisterForwardingAsync();
}
else
{
var tos = _handlerStack.Last();
Debug.Assert(tos != null);
if (handlerFactory.Equals(tos))
{
await _dispatchForwarding.RegisterForwardingAsync();
return;
}
if (tos is IDeactivationNotifyable notifyable)
{
await notifyable.NotifyDeactivationAsync();
}
_handlerStack = _handlerStack.Remove(handlerFactory);
await PushHandler(handlerFactory);
await _dispatchForwarding.RegisterForwardingAsync();
}
}
}
/// <summary>
/// Asynchronously registers a handler.
/// </summary>
/// <param name="handlerFactory">The handler to register.</param>
/// <returns>A task representing the asynchronous operation.</returns>
/// <exception cref="ArgumentNullException">Thrown if <paramref name="handlerFactory"/> is null.</exception>
public async Task RegisterAsync(IContextualProvider <THandler> handlerFactory)
{
if (handlerFactory == null)
{
throw new ArgumentNullException(nameof(handlerFactory));
}
Debug.Assert(_handlers != null);
Debug.Assert(_lock != null);
using (await _lock.LockAsync())
{
var handlers = _handlers.Add(handlerFactory);
if (handlers == _handlers)
{
return;
}
if (_handlers.IsEmpty)
{
await _dispatchForwarding.RegisterForwardingAsync();
}
if (_handlers.Count == 1 && _handlers.First() is IDeactivationNotifyable deactivationNotifyable)
{
await deactivationNotifyable.NotifyDeactivationAsync();
}
_handlers = handlers;
if (handlers.Count == 1 && handlerFactory is IActivationNotifyable activationNotifyable)
{
await activationNotifyable.NotifyActivationAsync();
}
}
}