title: System Query Option $filter in OData v4 (canonical functions)
body: <p>According to this documentation: <a href="http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part2-url-conventions/odata-v4.0-errata02-os-part2-url-conventions-complete.html#_Toc406398094" rel="nofollow">http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part2-url-conventions/odata-v4.0-errata02-os-part2-url-conventions-complete.html#_Toc406398094</a>
  I should be able to pass with $filter parameter queries like "$filter=contains(PropertyName, 'SomeValue')".</p>
  
  <p>When I pass logical operators (for example: 
  $filter=PropertyName eq 'SomeValue') it works fine. But functions like 'contains', 'substring', 'endswith', 'startswith' etc. never works -- query results from applying ODataQueryOptions to DbSet are always an empty set.</p>
  
  <p>Any ideas why?</p>