How to communicate from angular-material2 dialog to its parent : <p>I have <code>Parent</code> component that opens an <code>angular-material2</code> dialog box. </p>

<pre><code>let dialogRef = this.dialog.open(Child, {
            disableClose: true
        });
</code></pre>

<p>opened dialog <code>Child</code> component has a button 'Add'. I want to notify the `Parent' component if user click on 'Add' button. </p>

<p>How is this possible?</p>
