title: how to use entity framework to group by date not date with time
body: <p>my code:</p>
  
  <pre><code>//get data
  var myData = from log in db.OperationLogs
                group log by log.CreateTime.Date  into g
                orderby g.Key
                select new { CreateTime = g.Key, Count = g.Count() };
  </code></pre>
  
  <p>this code will throw an exception like entity framework does not support get Date operation.
  because <code>log.createtime</code> both have date and time, i want to group by date, how should i do</p>