title: How can I add an item to a IEnumerable<T> collection?
body: <p>My question as title above. For example</p>
  <pre class="lang-cs prettyprint-override"><code>IEnumerable&lt;T&gt; items = new T[]{new T(&quot;msg&quot;)};
  items.ToList().Add(new T(&quot;msg2&quot;));
  </code></pre>
  <p>but after all it only has 1 item inside. Can we have a method like <code>items.Add(item)</code> like the <code>List&lt;T&gt;</code>?</p>