Event handler and null-conditional operator
<p>For example, implement <code>INotifyPropertyChanged</code> interface:</p>

<pre><code>public event PropertyChangedEventHandler PropertyChanged;

private void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
    var handler = PropertyChanged;
    if (handler != null)
        handler.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
</code></pre>

<p>Two things:</p>

<ol>
<li>Copy event to local variable to prevent errors with multithreading (<a href="https://stackoverflow.com/questions/672638/use-of-null-check-in-event-handler">here</a> are some examples). Resharper gives notification, if you don't copy to local variable: </li>
</ol>

<p><a href="https://i.stack.imgur.com/sgqCq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/sgqCq.png" alt="Possible NullReferenceException"></a>  </p>

<ol start="2">
<li>Check it for null, to prevent <code>NullReferenceException</code></li>
</ol>

<p>But now, we can use <code>?.</code> operator for null-checking. And if I use it, Resharper is idle:
<a href="https://i.stack.imgur.com/KXO9Q.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/KXO9Q.png" alt="No errors"></a></p>

<p>So, question is: should I copy event <code>ProperyChanged</code> to local variable, if I use null-conditional operator?</p>