Question

I have a such situtation:

        foreach (var item in listBoxFileNames.SelectedItems)
        {
            MessageBox.Show("I am not waiting");
            CancellationTokenSource tokenSourcve = new CancellationTokenSource();
            CancellationToken token = tokenSourcve.Token;

            Task task1 = new Task(() =>
                {
                    ProcessDatas(); // method
                }
                , token);

            task1.Start();
        }

I want to make foreach to wait task’s completion. BUt it is not waiting. It showing me MessageBox immediately after each messagBox.

Answer 1

Yes, you’re starting the task, which will then execute in the background. If you want the loop to behave entirely synchronously, just call ProcessDatas() not in a task at all. You could start it and then wait for it to finish – but it’s not clear what benefit that would give you.

If you want to start all the tasks in parallel, but then wait for them afterwards, you could create a List<Task> and then call Task.WaitAll – or just use Parallel.ForEach to start with.