gistfile1.cs

namespace AsyncDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            new Program().Run();
            Console.WriteLine("Press any key to exit...");
            Console.ReadLine();
        }

        public async void Run()
        {
            await Process.Start("Notepad.exe");
            Console.WriteLine("Notepad was finished");
        }
    }

    public static class AwaiterExtensions
    {
        public static TaskAwaiter<int> GetAwaiter(this Process that)
        {
            var tcs = new TaskCompletionSource<int>();
            that.EnableRaisingEvents = true;
            that.Exited += (s, e) => tcs.TrySetResult(that.ExitCode);
            if (that.HasExited) tcs.TrySetResult(that.ExitCode);
            return tcs.Task.GetAwaiter();
        }
    }
}