using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

class Program
{
    static void Main(string[] args)
    {
        WaitAndDisplayException("From async method", ThrowMultipleAsync());
        WaitAndDisplayException("From manual method", ThrowMultipleManually());
    }

    static void WaitAndDisplayException(string name, Task t)
    {
        Console.WriteLine("Waiting for {0}", name);
        try
        {
            t.Wait();
            Console.WriteLine("Oops... it completed without throwing");
        }
        catch (AggregateException e)
        {
            Console.WriteLine("Thrown exception: {0}", FormatAggregate(e));
            Console.WriteLine();
            Console.WriteLine("Task exception: {0}", FormatAggregate(t.Exception));
        }
        Console.WriteLine();
        Console.WriteLine();
        Console.WriteLine();
    }

    static string FormatAggregate(AggregateException e)
    {
        return string.Format("{0} error(s):\r\n{1}", e.InnerExceptions.Count,
            string.Join("\r\n", e.InnerExceptions.Select(x => x.Message)));
    }

    static async Task ThrowMultipleAsync()
    {
        Task t1 = DelayedThrow(500);
        Task t2 = DelayedThrow(1000);
        await TaskEx.WhenAll(t1, t2);
    }

    static Task ThrowMultipleManually()
    {
        Task t1 = DelayedThrow(500);
        Task t2 = DelayedThrow(1000);
        return TaskEx.WhenAll(t1, t2);
    }

    static Task DelayedThrow(int delayMillis)
    {
        return TaskEx.Run(delegate {
            Thread.Sleep(delayMillis);
            throw new Exception("Went bang after " + delayMillis);
        });
    }
}