title: C# list<item> group by year then by month
body: <p>I have a List and Item contains one property called Created which is DateTime.</p>
  
  <p>How can I group the items by Year then by month in descending order like this?</p>
  
  <pre><code>2015
      August
      July
      June
      May
      April
      March
      February
      January
  2014
      December
      November
      October
  ........
  </code></pre>
  
  <p>Here is my approach:</p>
  
  <pre><code>var grouped = myList.GroupBy(t =&gt; t.Created.Year).Select(t =&gt; new { Year = t.Key, Months = t.GroupBy(x =&gt; x.Created.Month) });
  </code></pre>