An expert in PLINQ for a day

One of the nice things about writing a book is that you become an expert on a subject (albeit in my case, just for a very short time). At the moment I know exactly how to make different parts of a Parallel Language Integrated Query (PLINQ) expression sequential so that the order of the output set is the one that you want. 

Not many people can say this.  (Oh, and PLINQ is a very neat technology by the way).