using System;

using System.Threading.Tasks;

​

public class Program

{

    public static async Task Main()

    {       

        var tasks = new Task[10];

        for (int i = 0; i < tasks.Length; i++)

        {

            tasks[i] = Task.Run(() => Console.WriteLine(IdGenerator.GetNextId()));

        }

        await Task.WhenAll(tasks);

    }

}

​

public static class IdGenerator

{   

    public static int GetNextId()

    {

        // TODO

        return 0;

    }

}