title: Linq group by bahaving strangely
body: <p>I have a simple list of int with three elements, all of them are set to 1000.
  If I group this list by values, I still get three elements instead of just one. 
  Why?</p>
  
  <pre><code>var l = new List&lt;int&gt; {1000, 1000, 1000};
  var gr = from i in l
           group i by new
              {
                  j = i
              }
              into g1
              from g in g1
              select new
              {
                  Id = g1.Key.j
              };
  
  var count = gr.Count(); // &lt;- count is 3!
  </code></pre>