How to change each element of a List<long>?
<p>I have a List of different DayTime (Ticks). I try to get a list of the time remaining from now to each time element.</p>

<pre><code>List&lt;long&gt; diffliste = new List&lt;long&gt;(m_DummyAtTime);

// 864000000000 ≙ 24h
diffliste.ForEach(item =&gt; { item -= now; if (item &lt; 0) item += 864000000000; }); 

// test, does also not work
// diffliste.ForEach(item =&gt; { item -= 500; }); 
</code></pre>

<p>However, the list is not changed. Do I miss something?
(<code>now</code> is <code>DateTime.Now.TimeOfDay.Ticks</code>)</p>
