Hi Viktor,
Using .AsEnumerable() and .AsQueryable() to cut over to a memory-bound collection has the same fundamental drawback as using .ToList() in my scenario - it still presumes I have access to the builder service and can inject behaviour between the filter and projection steps. I don't have that access in my scenario, which means I am stuck with the really inefficient query that you described or somehow rebuilding my external tool.
While I recognize that this is a strange projection to construct in a database-bound scenario, I don't feel it is an unreasonable one. Is it possible that this projection will be possible in future versions of Telerik Data Access?