Thank you, I think I get it. Async spawns processes more of “on demand” rather than preemptively; i.e. if no blocking operation is encountered then no process is spawned? So a loop with say 100 function calls where only 3 of them get blocked would in essence only use 4 threads instead of 101 if it had been coded as multi-threaded?

Well, the most important fact here is that with async you can handle multiple requests at the same time, just if any of those requests reach a blocking operation, they don’t block the used thread, instead, the thread is returned for some other request to use it. But once the blocking operation is done a new thread is assigned to the waiting request so it could be finished (that’s why you see thread 1 as an entry and thread 11,18… as output – this is why I said that async is using multiple threads in my previous reply). That’s the main point of async operations.

Thank you, I was discussing this with a colleague who insisted that async did not use multiple threads, which is one way to interpret articles like this discussing the differences. My takeaway is rather that with async you don’t control the spawned threads you only get their results whereas with multi-threading you keep control the whole time. There are always multiple threads involved, the difference is how many are “yours”. Is that a fair conclusion?

Hello Mats. Of course, both examples use multiple threads. As you wrote the last sentence, in the first example, with async the initial thread is always returned to the thread pool (when your code is waiting for some other execution), and then after a new thread is assigned to that request to finish the process. That’s why you see thread 1 for all three requests and different thread numbers once these requests are done. So, both examples are multithreaded, just in the first case, the thread is returned to the thread pool and that same thread can be assigned to another request while the first request is waiting for other executions.

IMO, the type of application is irrelevant here. The concept is what matters. Also, we talked a bit about synchronization context here: https://code-maze.com/asynchronous-programming-with-async-and-await-in-asp-net-core/

But as you will see, we don’t have it in the ASP.NET Core apps.

Hello Bac Vo. Thanks. Regarding your question, maybe you can find some answers here