Visual Studio Code – Async method in web-app does not complete if it is not awaited – execution just steps back out into the controller. Why?

I have a simple web app, built with .NET Core (3.1) MVC and EF Core 5, containing a PersonController and a PersonService. (The project was provided by a teacher in my educational program, and he doesn’t understand why the problem occurs either.) I work with VS2019.

The PersonController contains a constructor initializing a PersonService, and a delete-method:

public PersonController(IPersonService personService)
{
    _PersonService = personService;
}

[HttpPost, ActionName("Delete")]
public async Task<IActionResult> DeleteConfirmed(int id)
{
    _ = _PersonService.DeleteAsync(id);

    TempData["Message"] = "successfully deleted";

    return RedirectToAction("Index");
}

The PersonService contains a DbContext and the DeleteAsync() method:

private readonly MyContext _context;

public async Task DeleteAsync(int? id)
{
    Person person = await _context.People.FindAsync(id);
    _context.Remove(person);
    await _context.SaveChangesAsync();
}

The problem:

The person is not removed from the database. When debugging, _PersonService.DeleteAsync(id) is called, the method executes until _context.Remove(person) but await _context.SaveChangesAsync() never gets executed. The execution returns to the calling method, and the TempData message shows up. The person-entry is not deleted from the database. This is the first time I’ve seen Visual Studio step out of a method before completion.

I can resolve this problem when I replace the Discard _ = with await. In this case, the code executes as expected — but I’ve read that "fire and forget" can be totally fine under the right circumstances.

I’ve also read that controllers are discarded after each request – but when the method in the PersonService stops executing, the debugger is still in the controller (at the TempData), so it seems that this can’t be the reason.

Can someone explain what’s causing the method to stop executing before it’s done? Or alternatively, maybe you could tell me how I can find out what’s happening in the background by using some feature of the debugger I’m unaware of, or something like that?