title: Groupby multiple date properties by month and year in LINQ
body: <p>I need to group by multiple properties by month and year in <code>C#</code> <code>LINQ</code></p>
  
  <p>This is my code:</p>
  
  <pre><code>public class Class1
  {
      public Nullable&lt;DateTime&gt; dt1 { get; set; }
      public Nullable&lt;DateTime&gt; dt2 { get; set; }
  }
  
  Class1 obj1 = new Class1 { dt1 = new DateTime(2012, 11, 12),
                             dt2 = new DateTime(2012, 12, 12) };
  Class1 obj2 = new Class1 { dt1 = new DateTime(2012, 11, 12),
                             dt2 = new DateTime(2012, 12, 12) };
  Class1 obj3 = new Class1 { dt1 = null, dt2 = new DateTime(2012, 10, 12) };
  Class1 obj4 = new Class1 { dt1 = new DateTime(2012, 10, 12), dt2 = null };
  Class1 obj5 = new Class1 { dt1 = null, dt2 = new DateTime(2012, 11, 12) };
  Class1 obj6 = new Class1 { dt1 = new DateTime(2013, 10, 12), dt2 = null };
  
  List&lt;Class1&gt; listGoogleTimezone = new List&lt;Class1&gt;
  {
      obj1,
      obj2,
      obj3,
      obj4,
      obj5,
      obj6
  };
  </code></pre>
  
  <p>My required result to be like this </p>
  
  <pre><code>MONTH YEAR   COUNT
  </code></pre>
  
  
  
  <pre><code>OCT   2012   2
  NOV   2012   3
  DEC   2012   2
  </code></pre>
  
  <p>Help me out</p>