tbf/TBF/Rig/RegisterReaders/PoseidonCmdStartStop/ProcessExtensions.cs

using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;

namespace TBF.Rig.RegisterReaders.PoseidonCmdStartStop
{
    public static class ProcessExtensions
    {
        public static Task WaitForExitAsync(this Process process, CancellationToken cancellationToken = default)
        {
            if (process == null) throw new ArgumentNullException(nameof(process));
            if (process.HasExited) return Task.CompletedTask;

            var tcs = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);

            EventHandler handler = null;
            handler = (s, e) =>
            {
                try { tcs.TrySetResult(null); }
                finally { process.Exited -= handler; }
            };

            process.EnableRaisingEvents = true;
            process.Exited += handler;

            if (cancellationToken.CanBeCanceled)
            {
                cancellationToken.Register(() =>
                {
                    tcs.TrySetCanceled(cancellationToken);
                    process.Exited -= handler;
                });
            }

            return tcs.Task;
        }
    }
}