Implementing the Producer Consumer Pattern with TPL Dataflow

A while back I wrote a post about constraining the number of threads when you are working through a bunch of tasks in parallel. For example, if I have 1000 items in a list that I want to process, but I only want to work on 5 at a time, then any of the techniques I discussed there can be used (and you can also use the newer Parallel.ForEachAsync method).