This is a guess without seeing any of the exceptions:
You (ie., some committer to NH) probably worked around a missing expression
parser for Queryable.Aggregate in a previous version of re-linq by handling
the respective MethodCallExpressions in an expression visitor. In the
current version, re-linq now recognizes the Aggregate methods as query
operators and converts them into
AggregateResultOperator/AggregateFromSeedResultOperator instances (similar
to what it does for all query operators).
This means the code previously handling the MethodCallExpressions for
Queryable.Aggregate should now be rewritten to handle the result operators
instead.
In general, whenever you have a query operator that's not detected by
re-linq, please don't write code handling the MethodCallExpressions
directly, but instead add an expression parser (IExpressionNode
implementation) for that method. This approach has several advantages, among
others that you avoid breaking your code with later versions of re-linq. See
my blog post (
https://www.re-motion.org/blogs/mix/archive/2010/10/28/re-linq-extensibility-custom-query-operators.aspx),
and post to the re-motion-users mailing list if there are any
questions/problems (or if re-linq is missing a standard query operator).
(Out of curiosity: If I'm guessing correctly, _how_ do you actually
translate the Aggregate query operator to HQL? After all, the aggregation
function could contain completely arbitrary code...)
Regards,
Fabian
