Async all the way vs. Task.Run on a simple calculation method

Question

I've started to dive into aync programming and I want to execute a very simple add method as an async operation.

One of the things i've read is that truly async program does not require thread switching => that means Task.Run(..) can be avoided.

This is how I've implemented an add method:

public class TaskSimpleExample
    {
        public static void SimpleCalcExample()
        {
            // Will perform in background
            Task<int> resultTask = Task.Run(() => BeginCalcNumbers(6, 6));
            Console.WriteLine("Doing Work");
            Console.WriteLine("Doing More Work");
            Console.WriteLine("Doing Extra Work");
            resultTask.Wait();
            Console.WriteLine("Work is done!");
        }

        static int BeginCalcNumbers(int number1, int number2)
        {
            int result = Add(number1, number2);
            Console.WriteLine(result);
            return result;
        }

        static int Add(int number1, int number2)
        {
            int result = number1 + number2;
            return result;
        }
    }

Unfortunately, I understand that it has nothing to do with async . It just opens another thread and runs in the background.

I've failed to convert this code to use async & await (and eliminate Task.Run ). Is it possible ? (Please notice I need to continue after the callback in other place in the method using resultTask.Wait() ).

Answer 1

What you know about Task.Run is absolutely correct and that's pretty much the point of using Task.Run

Using Task.Run will execute a method on a thread pool thread and return a task that represents the completion of the method.

As Stepthen Cleary suggest, you should use Task.Run only to call CPU-bound methods.

Another important thing to mention is that you should use Task.Run to actually call the method that does heavy CPU-bound work and not use Task.Run in the implementation of the method.

Here's a good example on how to use Task.Run properly:

class MyService
{
  public int CalculateMandelbrot()
  {
    // Tons of work to do in here!
    for (int i = 0; i != 10000000; ++i)
      ;
    return 42;
  }
}

...

private async void MyButton_Click(object sender, EventArgs e)
{
  await Task.Run(() => myService.CalculateMandelbrot());
}

Also you should read Task.Run Etiquette and Proper Usage and Task.Run Etiquette Examples: Don't Use Task.Run in the Implementation if you are interested in learning more about Task.Run