My needs
I would like our in house, standard product to fire different events when things happen. In global asax on different custom solutions, I would like to hookup on these events, when needed, and react.
Existing modules
I have been looking for an event aggregator for asp.net but I'm not really sure what to use. I have read about Prism, but it seems, that this targets WPF/Silverlight and not asp.net.
Then there is this guy, who seems to have ported the aggregator into his own version, independent of WPF: http://weblogs.asp.net/rashid/archive/2009/03/05/use-event-aggregator-to-make-your-application-more-extensible.aspx
Question
Have anyone experiences using an event aggregator for asp.net? This is for production use, so I prefer not to use some home-coded aggregator from a random guy on the net :)
Thankyou in advance.
EDIT 1: It seemed, that NServiceBus was a little overkill for the purpose. I created a single EventAggregator class that does the trick.
The class:
/// <summary>
/// A event aggregator.
/// </summary>
public class EventAggregator
{
/// <summary>The object to use when locking.</summary>
private readonly object _lock = new object();
/// <summary>Holder of registered event handlers</summary>
private readonly Dictionary<Type, List<object>> _handlers = new Dictionary<Type, List<object>>();
/// <summary>Registers the specified handler.</summary>
/// <typeparam name="T"></typeparam>
/// <param name="handler">The handler.</param>
public void Register<T>(EventHandler<T> handler) where T : EventArgs
{
lock (_lock)
{
if (!_handlers.ContainsKey(typeof (T)))
_handlers.Add(typeof (T), new List<object>());
_handlers[typeof (T)].Add(handler);
}
}
/// <summary>Publishes the specified event.</summary>
/// <typeparam name="T"></typeparam>
/// <param name="sender">The sender.</param>
/// <param name="eventToPublish">The event to publish.</param>
public void Publish<T>(object sender, T eventToPublish) where T : EventArgs
{
lock (_lock)
{
if (!_handlers.ContainsKey(typeof (T)))
return; // No listers for event
foreach (EventHandler<T> handler in _handlers[typeof (T)])
handler.Invoke(sender, eventToPublish);
}
}
}
An event class:
public class EntityDeleted : EventArgs
{
}
Registering an event handler in global asax:
aggregator.Register<EntityDeleted>((s, e) => {
// Do stuff here
});
Raising an event:
aggregator.Publish(this, new EntityDeleted());
EDIT 2:
And here are my unit test for the ones interrested:
/// <summary>
/// Unit tests for EventAggregator
/// </summary>
[TestClass]
public class EventAggregatorTest
{
/// <summary>Tests that no exceptions are thrown when calling an event with no handlers.</summary>
[TestMethod]
public void EmptyAggregatorTest()
{
var aggregator = new EventAggregator();
aggregator.Publish(this, new TestEventOne() { Property = "p1" });
}
/// <summary>Tests the aggregator using a single, registered handler.</summary>
[TestMethod]
public void SingleListenerTest()
{
var aggregator = new EventAggregator();
int calls = 0;
aggregator.Register<TestEventOne>((sender, e) =>
{
Assert.AreEqual("p1", e.Property);
calls ++;
});
Assert.AreEqual(0, calls);
aggregator.Publish(this, new TestEventOne(){Property = "p1"});
Assert.AreEqual(1, calls);
}
/// <summary>Tests the aggregator using multiple registered handlers.</summary>
[TestMethod]
public void MultipleListenersTest()
{
var aggregator = new EventAggregator();
int p1Calls = 0;
int p2Calls = 0;
aggregator.Register<TestEventOne>((sender, e) =>
{
Assert.AreEqual("p1", e.Property);
p1Calls++;
});
aggregator.Register<TestEventOne>((sender, e) =>
{
Assert.AreEqual("p1", e.Property);
p1Calls++;
});
aggregator.Register<TestEventTwo>((sender, e) =>
{
Assert.AreEqual("p2", e.Property);
p2Calls++;
});
Assert.AreEqual(0, p1Calls);
aggregator.Publish(this, new TestEventOne() { Property = "p1" });
Assert.AreEqual(2, p1Calls);
Assert.AreEqual(0, p2Calls);
aggregator.Publish(this, new TestEventTwo() { Property = "p2" });
Assert.AreEqual(1, p2Calls);
Assert.AreEqual(2, p1Calls);
}
}
/// <summary>
/// Dummy test event 1
/// </summary>
public class TestEventOne : EventArgs
{
public string Property { get; set; }
}
/// <summary>
/// Dummy test event 2
/// </summary>
public class TestEventTwo : EventArgs
{
public string Property { get; set; }
}
EDIT 3:
Thanks to Steven Robbins for pointing out, that the aggregator was not thread safe, I added locking to the Publish and Register methods.
