title: How to change each element of a List<long>?
body: <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>