Скачать или смотреть Working Software ep. 7: Aggregating Sequences in .NET

Following the previous episode, in which we have talked about using LINQ in design, in this episode we will turn our focus to one corner case which plagues LINQ - deferred aggregation of sequences. You will see one genuine problem which occurs in real world applications, and one attempt to solve it.
The problem we will outline appears when working with a stream of objects which is never materialized into a collection, with twofold request: One is to pass the stream through an operator which consumes it, and other is to calculate one or more aggregated values on it.
While existing Aggregate LINQ operator consumes the sequence, hence making it unavailable to any subsequent operator, in this presentation, you will see a modified Aggregate operator which accumulates information along with execution of an unrelated LINQ operator: A deferred aggregation - the missing feature of LINQ.