Using an IEnumerable of custom objects, returned from a LINQ to Entities query, I get an "operation not implemented" error in my report viewer, unless I iterate through the list first, e.g. by calling ToList() on it.
I already do this on the source query from entities, then I query the results using custom methods etc. for calculations.
Why is this initial iteration required for some clients, e.g. the telerik report? This isn't the only place I've seen this requirement.