Dynamically change TPL Dataflow Block MaxDegreeOfParallelism

Question

When I create a Dataflow Block I specify its MaxDegreeOfParallelism like this:

...New ExecutionDataflowBlockOptions With 
   {.MaxDegreeOfParallelism = System.Environment.ProcessorCount - 1}...

Is any way to change it later?

Answer 1

No, you can't do that.

What you can do is to create the block with a high enough MDOP (possibly Unbounded) and use SemaphoreSlim to limit the degree of parallelism to what you actually want.

Then, when you want to change the degree of parallelism, call Release(int releaseCount) (to increase it) or await WaitAsync() in a loop (to decrease it).