2010->2012 query generation issue

I had code like this:

case FilterChoice.Contains:
                        predicates.Add(PredicateBuilder.Make(typeof(T), filterBoxRow.FieldName, FilterOperator.Contains, filterBoxRow.GetFilterFrom()));
                        break;

Basically, I'm building filter manually. If there is empty string it generates WHERE statement like this:

WHERE ( CAST(CHARINDEX(LOWER(N''), LOWER([Extent1].[UserName])) AS int)) > 0

And it effectively filter's out whole thing.. I think it should do "LIKE '%%'" ?

katit, FilterOperator.Contains will be translated into a SQL LIKE clause if the "IgnoreCase" option on the PredicateDescription is turned off.  By default it's on, so a ToLower method is added to both the property and value clauses, which in turn causes EF to  translate the expression using the SQL CharIndex method.