Make ThreadPool replaceable with own + introduce IThreadPool instead of SynchronizationContext

[sidristij]

Now we cannot use own pools as default and name "SynchronizationContext" means nothing in pooling context. I mean, if somebody who trying to learn how to work with threads and threads pooling see SynchronizationContext, no one will say: "ahh, this is abstraction layer for accessing some ThreadPool, ok". No. SyncContext is some place.... where what? I should synchronize some context with who?

1. I suggesting to add type IThreadPool instead of use SynchronizationContext
2. I understand that it is impossible to make ThreadPool non-static. So, I suggest to add method ThreadPool.ReplaceImplementation(IThreadPool pool); And for every method, which allows to run something in parallel, make additional parameter "IThreadPool targetPool = default" to pass concrete model of parallelism.

[Clockwork-Muse]

A thread pool and synchronization context do different things.

That aside, generally you don't want or need to create your own thread pool - usually you'd create and use a TaskScheduler instead. This is a fairly advanced usage, though, are you sure you need to do this?

[sidristij]

Disagree with you. TaskScheduler is for Tasks. It can cover SynchronizationContext to work on some thread pool. Which can be regular ThreadPool, user-defined threadpool or single thread threadpool: for example, on UI SynchronizationContext. SynchronizationContext is abstraction layer of threadpool. TaskScheduler.FromCurrentSynchronizationContext