title: C# Event handlers are not available to another reference
body: <p>I have an example class. It has an ObservableCollection with an event handler attached.</p>
  <pre><code>class SomeItem
  {
      public ObservableCollection&lt;Thing&gt; Things = new ObservableCollection&lt;Thing&gt;();
      
      private SomeEventHandler(object Sender, NotifyCollectionChangedEventArgs E)
      {
          //do something
      }
      
      public SomeItem()
      {
          this.Things.CollectionChanged += SomeEventHandler;
      }
  }
  </code></pre>
  <p>I'm executing the following code:</p>
  <pre><code>SomeItem Instance = new SomeItem();
  
  Instance.Things.Add(new Thing()); // SomeEventHandler executed;
  
  SomeItem AnotherReference = Instance;
  
  AnotherReference.Things.Add(new Thing()); // SomeEventHandler NOT executed
  </code></pre>
  <p>Why the event handler not being executed if collection is accessed from <strong>AnotherReference</strong>?</p>