Update event aggregator pattern examples

Author: nemanjarogic

src/AdditionalPatterns/EventAggregator/StoreManagement/Components/EventAggregator.cs

@@ -68,7 +68,8 @@ public IDisposable Subscribe<T>(ICustomObserver<T> newObserver)
     {
         if (!_typedObservers.TryGetValue(typeof(T), out List<IObserver<IEvent>> observers))
         {
-            observers = _typedObservers[typeof(T)] = new List<IObserver<IEvent>>();
+            observers = new List<IObserver<IEvent>>();
+            _typedObservers[typeof(T)] = observers;
         }
 
         return SubscribeAndSendEvents(observers, newObserver, _events.Where(evt => evt is T));

src/AdditionalPatterns/EventAggregator/StoreManagement/Components/Subscribers/BusinessTrackingSubscriber.cs

@@ -7,13 +7,11 @@ namespace StoreManagement.Components.Subscribers;
 /// </summary>
 public class BusinessTrackingSubscriber : ICustomObserver<IEvent>
 {
-    private readonly IEventAggregator _eventAggregator;
     private readonly IDisposable _unsubscriber;
 
     public BusinessTrackingSubscriber(IEventAggregator eventAggregator)
     {
-        _eventAggregator = eventAggregator;
-        _unsubscriber = _eventAggregator.Subscribe(this);
+        _unsubscriber = eventAggregator.Subscribe(this);
     }
 
     public void OnNext(IEvent @event)

src/AdditionalPatterns/EventAggregator/StoreManagement/Components/Subscribers/OrderSubscriber.cs

@@ -8,13 +8,11 @@ namespace StoreManagement.Components.Subscribers;
 /// </summary>
 public class OrderSubscriber : ICustomObserver<OrderCreatedEvent>
 {
-    private readonly IEventAggregator _eventAggregator;
     private readonly IDisposable _unsubscriber;
 
     public OrderSubscriber(IEventAggregator eventAggregator)
     {
-        _eventAggregator = eventAggregator;
-        _unsubscriber = _eventAggregator.Subscribe(this);
+        _unsubscriber = eventAggregator.Subscribe(this);
     }
 
     public void OnNext(IEvent @event) =>

src/AdditionalPatterns/EventAggregator/StoreManagement/Components/Unsubscriber.cs

@@ -21,7 +21,6 @@ public void Dispose()
         GC.SuppressFinalize(this);
     }
 
-    // The bulk of the clean-up code is implemented in Dispose(bool)
     protected virtual void Dispose(bool disposing)
     {
         if (_isDisposed)

src/AdditionalPatterns/EventAggregator/StoreManagement/Contracts/IEvent.cs

@@ -2,5 +2,5 @@
 
 public interface IEvent
 {
-    public string Description { get; set; }
+    public string Description { get; }
 }

src/AdditionalPatterns/EventAggregator/StoreManagement/Events/OrderCreatedEvent.cs

@@ -9,5 +9,5 @@ public OrderCreatedEvent(string description)
         Description = description;
     }
 
-    public string Description { get; set; }
-}
+    public string Description { get; }
+}

src/AdditionalPatterns/EventAggregator/StoreManagement/Events/WarehouseReceivedNewSuppliesEvent.cs

@@ -9,5 +9,5 @@ public WarehouseReceivedNewSuppliesEvent(string description)
         Description = description;
     }
 
-    public string Description { get; set; }
-}
+    public string Description { get; }
+}

src/AdditionalPatterns/EventAggregator/StoreManagement/Executor.cs

@@ -33,5 +33,11 @@ public override void Execute()
 
         Console.WriteLine("\nPreparing order 3...");
         orderPublisher.Publish("Order 3");
+
+        businessTrackingSubscriber.Unsubscribe();
+
+        // This event won't be handled, because there are no subscribers anymore.
+        Console.WriteLine("\nPreparing order 4...");
+        orderPublisher.Publish("Order 4");
     }
 }