gistfile1.txt

using System;
using System.Collections.Concurrent;
using System.Threading.Tasks;

// --- Action  ---

var actionQueue = new ActionQueue();

Console.WriteLine("No await");
for (int i = 0; i < 10; i++)
    actionQueue.PutOnQueue(() => DoAsync());
Console.ReadLine();

Console.WriteLine("Async await in lambda");
for (int i = 0; i < 10; i++)
    actionQueue.PutOnQueue(async () => await DoAsync());
Console.ReadLine();

Console.WriteLine("Wait() in lambda");
for (int i = 0; i < 10; i++)
    actionQueue.PutOnQueue(() => DoAsync().Wait());
Console.ReadLine();

// Console.WriteLine("Method group");
// Does not compile because DoSomething returns Task instead of void: actionQueue.PutOnQueue(DoSomething);
// Console.ReadLine();

// --- Func<Task> ---

var funcOfTaskQueue = new FuncOfTaskQueue();

Console.WriteLine("No await");
for (int i = 0; i < 10; i++)
    funcOfTaskQueue.PutOnQueue(() => DoAsync());
Console.ReadLine();

Console.WriteLine("Async await in lambda");
for (int i = 0; i < 10; i++)
    funcOfTaskQueue.PutOnQueue(async () => await DoAsync());
Console.ReadLine();

// Console.WriteLine("Wait() in lambda");
// for (int i = 0; i < 10; i++)
// Does not compile because Wait() does not return a Task: funcOfTaskQueue.PutOnQueue(() => DoSomething().Wait());
// Console.ReadLine();

Console.WriteLine("Method group");
for (int i = 0; i < 10; i++)
    funcOfTaskQueue.PutOnQueue(DoAsync);
Console.ReadLine();

async Task DoAsync()
{
    Console.WriteLine("Start of method");

    await Task.Delay(100);

    Console.WriteLine("End of method");
}

class ActionQueue
{
    BlockingCollection<Action> _queue = new();

    public ActionQueue()
        => _ = Task.Run(QueueHandlingLoop);

    private void QueueHandlingLoop()
    {
        foreach (var action in _queue.GetConsumingEnumerable())
        {
            action();
        }
    }

    public void PutOnQueue(Action action) {
        _queue.Add(action);
    }  
}

class FuncOfTaskQueue
{
    BlockingCollection<Func<Task>> _queue = new();

    public FuncOfTaskQueue()
        => _ = Task.Run(QueueHandlingLoop);

    private async Task QueueHandlingLoop()
    {
        foreach (var action in _queue.GetConsumingEnumerable())
        {
            await action();
        }
    }

    public void PutOnQueue(Func<Task> action)
    {
        _queue.Add(action);
    }
}