AwaitInArgumentList.cs

using System;
using System.Threading.Tasks;

namespace ArgumentListAwait
{
    class Program
    {
        // Too bad to call a function with multiple task results you have to
        // store the intermediate tasks in locals because of the order of
        // evaluation of argument lists.
        static void Main(string[] args)
        {
            // Slow
            //
            // +A
            // -A
            // +B
            // -B
            // +C
            // -C
            // Called
            Task.Run(
                async () =>
                {
                    await Argumentative(
                        await LoudDelay("A"),
                        await LoudDelay("B"),
                        await LoudDelay("C"));
                }).Wait();

            // Fast:
            //
            // +A
            // +B
            // +C
            // -C
            // -A
            // -B
            // Called
            Task.Run(
                async () =>
                {
                    var a = LoudDelay("A");
                    var b = LoudDelay("B");
                    var c = LoudDelay("C");
                    await Argumentative(
                        await a,
                        await b,
                        await c);
                }).Wait();
        }

        static Task Argumentative(
            params object[] p)
        {
            Console.WriteLine("Called");
            return Task.CompletedTask;
        }

        static async Task<object> LoudDelay(
            string id)
        {
            Console.WriteLine($"+{id}");
            await Task.Delay(TimeSpan.FromSeconds(2));
            Console.WriteLine($"-{id}");
            return null;
        }
    }
}