How to implement thread pool?

Question

C++ / C#

The task was to simultaneously complete a bunch of small tasks, merge their results into one list. Additionally, you need to transfer data from the stream to the indicator form, I read that working with the gui from the stream is somehow done in a special way.
The task itself is new to me. In order to save time, recommend something sensible to read on the topic.

Answer 1

Googled about tasks and the Task.WhenAll method