title: Truncate DateTime in NHibernate QueryOver SelectGroup
body: <p>I have a fairly run-of-the-mill QueryOver query containing the following,</p>
  
  <pre><code>.SelectList(list =&gt; list
      .SelectGroup(() =&gt; txn.GroupField)
      .SelectGroup(() =&gt; txn.Date))
  .List&lt;object[]&gt;()
  </code></pre>
  
  <p>This query works as expected however I now have a requirement to group by the truncated Date as some of the Date's for these objects may contain a time component. This seems like it should be a trivial change but I can't find a way that is supported by NHibernate.</p>
  
  <p>The obvious solution would be the change below but is not supported.</p>
  
  <pre><code>.SelectGroup(() =&gt; txn.Date.Date))
  </code></pre>
  
  <p>Any ideas?</p>
  
  <p>Thanks</p>