Different behavior async/await in almost the same methods

Question

Let\'s say I have two async methods

public async static Task RunAsync1()
{
    await Task.Delay(2000);
    await Task.Delay(2000);
}

and

Answer 1

In the first case you are saying

public async static Task RunAsync1()
{
    var t1 = Task.Delay(2000);
    await t1;
    var t2 = await Task.Delay(2000);
    await t2;
}

Which equates to

1. 0:00 Create a callback in 2 seconds 0:00
2. 0:00 Wait until the callback has returned 0:02
3. 0:02 Create a callback in 2 seconds 0:02
4. 0:02 Wait until the callback has returned 0:04
5. 0:04 return;

The second case is

public async static Task RunAsync2()
{
    var t1 = Task.Delay(2000);
    var t2 = Task.Delay(2000);

    await t1;
    await t2;
}

1. 0:00 Create callbacks in 2 seconds 0:00
2. 0:00 Create callbacks in 2 seconds 0:00
3. 0:00 Wait for first callback 0:02
4. 0:02 Wait for the second callback 0:02
5. 0:02 return

In other words, in the first one you are doing sequential asynchronous programming, and the second is parallel asynchronous programming.