EventAggregator, is it thread-safe?
- by pfaz
Is this thread-safe?
The EventAggregator in Prism is a very simple class with only one method. I was surprised when I noticed that there was no lock around the null check and creation of a new type to add to the private _events collection. If two threads called GetEvent simultaneously for the same type (before it exists in _events) it looks like this would result in two entries in the collection.
/// <summary>
/// Gets the single instance of the event managed by this EventAggregator. Multiple calls to this method with the same <typeparamref name="TEventType"/> returns the same event instance.
/// </summary>
/// <typeparam name="TEventType">The type of event to get. This must inherit from <see cref="EventBase"/>.</typeparam>
/// <returns>A singleton instance of an event object of type <typeparamref name="TEventType"/>.</returns>
public TEventType GetEvent<TEventType>() where TEventType : EventBase
{
TEventType eventInstance = _events.FirstOrDefault(evt => evt.GetType() == typeof(TEventType)) as TEventType;
if (eventInstance == null)
{
eventInstance = Activator.CreateInstance<TEventType>();
_events.Add(eventInstance);
}
return eventInstance;
}
