async-enumerable.cs

static async Task Main(string[] args)
{
    await foreach (var num in  GenerateNumbersAsync())
    {
        Console.WriteLine(num);
    }

    Console.ReadLine();
}

public static async IAsyncEnumerable<int> GenerateNumbersAsync()
{
    for (int i = 0; i < 100; i++)
    {
        await Task.Delay(TimeSpan.FromSeconds(1));

        yield return i;
    }
}