using System;

using System.Threading.Tasks;

using System.Collections.Generic;

public class Program

{

    private static Random _rand = new Random();

    public static void Main()

    {

        Example1().ConfigureAwait(false).GetAwaiter().GetResult();

        Example2().ConfigureAwait(false).GetAwaiter().GetResult();

    }

    public static async Task Example1()

    {

        var s = new Queue<string>(new[] {"foo", "bar", "baz"});

        // example usage (inline lambda)

        await WaitUntil(() => s.Dequeue() == "bar");

​

        var shouldBeBaz = s.Dequeue();

        Console.WriteLine($"Should be 'baz': {shouldBeBaz}");

    }

    public static async Task Example2()

    {

        // example usage (function pointer)

        await WaitUntil(EncounteredMultipleOf2);

        Console.WriteLine("Found multiple of 2!");

    }

    private static bool EncounteredMultipleOf2()

    {

        return _rand.Next() % 2 == 0;

    }

    public static async Task WaitUntil(Func<bool> condition, int frequency = 25, int timeout = -1)

    {

        var waitTask = Task.Run(async () =>

        {

            while (!condition()) await Task.Delay(frequency);

        });

​

        if (waitTask != await Task.WhenAny(waitTask, 

                Task.Delay(timeout))) 

            throw new TimeoutException();

    }

}