Strings are not getting concatenated properly : <p>i have below code where string dont get concatenated</p>

<pre><code>string postCode = "1245";
string city = "Stockholm";
string postCodeAndCity = postCode ?? " " + " " + city ?? " ";
</code></pre>

<p>I get output as <strong>1245</strong>. Not sure why it excludes city.</p>

<p>But this line works</p>

<pre><code>string.Concat(postCode??" ", " ", city?? " ");
</code></pre>

<p>so why the first approach dont work?</p>
