using System;

using System.Reactive;

using System.Reactive.Linq;

using System.Threading.Tasks;

​

public class Program

{

    public static async Task Main()

    {

        Observable

            .Timer(TimeSpan.FromMilliseconds(100))

            .Finally(() => throw new ApplicationException("Oops!"))

            .Subscribe(_ => { }, ex => Console.WriteLine(ex.Message),

                () => Console.WriteLine("Completed"));

​

        await Task.Delay(1000);

    }

}

​