Passing Task as parameter to be invoked within loop in async method C#

Question

I have the following code in LINQPad:

async Task Main()
{
    await PrintLoop(Print1());
}

async Task Print1()
{
    Debug.WriteLine("Printing!");
}

//Print 2
//Print 3
//etc.

async Task PrintLoop(Task printer, int iterations = 3)
{
    for (int i = 0; i < iterations; i++)
    {
        await printer;
    }
}

I can't for the life of me figure out why I get the following output:

Printing!

As opposed to "Printing." x3.

If I call Print1() directly within the loop I get the following output:

Printing!
Printing!
Printing!
Printing!

Which kind of makes sense but isn't what I want to do. Instead, I would like for Print1 (or whichever method is passed as task ) to be invoked iterations times.

Can someone help me understand what's up and down here? Thanks!

Answer 1

You are passing the result of calling Print1() to the method (a Task ). You aren't passing the method itself. So it's only called once at Print1() . When you await printer; , it's really just saying "yup, it happened" and moving on.

If you want to pass the method itself, so that it can be called inside PrintLoop , then you need to accept a Func<Task> (a method that returns a Task ).

Then you pass the method itself ( Print1 ) without calling it (not Print1() )

async Task Main()
{
    await PrintLoop(Print1); //not Print1()
}

async Task Print1()
{
    Debug.WriteLine("Printing!");
}

async Task PrintLoop(Func<Task> printer, int iterations = 3)
{
    for (int i = 0; i < iterations; i++)
    {
        await printer();
    }
}