CollectionChanged event gets executed for non associated object
<p>I have two ObservableCollection objects and obj1 has attach to collection change event. Obj1 has a value from obj2 by obj1 = obj2. When I add any item on obj2 it execute collection changed event of object 1. I could not understand why this is happening.</p>

<blockquote>
<pre><code> public MainWindow()
    {
        InitializeComponent();

        ObservableCollection&lt;int&gt; obj1 = new ObservableCollection&lt;int&gt;();
        ObservableCollection&lt;int&gt; obj2 = new ObservableCollection&lt;int&gt;();

        obj1 = obj2;

        obj1.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(obj1_CollectionChanged);

        obj2.Add(1);
</code></pre>
</blockquote>

<p>}</p>

<pre><code>    void obj1_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        MessageBox.Show("Testing");
    }
</code></pre>
