title: At least one object must implement IComparable?
body: <p>Model:</p>
  
  <pre><code>return (from m in meterReadings
         group m by new { date = m.ReadDate } into g
         select new
         {
             ReadDate = g.Key.date.ToString("dd.MM.yyyy - HH:mm:ss"),
             T1 = from t1 in g
                  where t1.Name == "T1"
                  select t1.Value.ToString("0,0.000"),
             T2 = from t2 in g
                  where t2.Name == "T2"
                  select t2.Value.ToString("0,0.000"),
             T3 = from t3 in g
                  where t3.Name == "T3"
                  select t3.Value.ToString("0,0.000"),
             Total = from total in g
                  where total.Name == "Toplam"
                  select total.Value.ToString("0,0.000")
         }).AsQueryable&lt;object&gt;();
  </code></pre>
  
  <p>Query</p>
  
  <pre><code>var table = MeterReadingManager.GetMeterReadingsPivot(meterReadings, 1);
  //No Error (in title)
  rows = table.OrderBy("ReadDate","desc").Skip((pageIndex) * pageSize).Take(pageSize)
  //Error  (in title)
  rows = table.OrderBy("T1","desc").Skip((pageIndex) * pageSize).Take(pageSize)
  </code></pre>
  
  <p>When I order by ReadDate, It works. But When I try to order by other fields I get the error : <code>At least one object must implement IComparable</code></p>
  
  <p>Why I get this error? And How can I fix it?</p>