Use https://github.com/Tyrrrz/CliWrap instead, the following code has some shortcomings

ProcessAsyncHelper.cs

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

// based on https://gist.github.com/AlexMAS/276eed492bc989e13dcce7c78b9e179d
public static class ProcessAsyncHelper
{
    public static async Task<ProcessResult> RunProcessAsync(string command, string arguments, int timeout)
    {
        var result = new ProcessResult();

        using (var process = new Process())
        {
            process.StartInfo.FileName = command;
            process.StartInfo.Arguments = arguments;
            process.StartInfo.UseShellExecute = false;
            //process.StartInfo.RedirectStandardInput = true;
            process.StartInfo.RedirectStandardOutput = true;
            process.StartInfo.RedirectStandardError = true;
            process.StartInfo.CreateNoWindow = true;

            var outputBuilder = new StringBuilder();
            var outputCloseEvent = new TaskCompletionSource<bool>();

            process.OutputDataReceived += (s, e) =>
            {
                if (e.Data == null)
                {
                    outputCloseEvent.SetResult(true);
                }
                else
                {
                    outputBuilder.Append(e.Data);
                }
            };

            var errorBuilder = new StringBuilder();
            var errorCloseEvent = new TaskCompletionSource<bool>();

            process.ErrorDataReceived += (s, e) =>
            {
                if (e.Data == null)
                {
                    errorCloseEvent.SetResult(true);
                }
                else
                {
                    errorBuilder.Append(e.Data);
                }
            };

            var isStarted = process.Start();
            if (!isStarted)
            {
                result.ExitCode = process.ExitCode;
                return result;
            }

            // Reads the output stream first and then waits because deadlocks are possible
            process.BeginOutputReadLine();
            process.BeginErrorReadLine();

            // Creates task to wait for process exit using timeout
            var waitForExit = WaitForExitAsync(process, timeout);

            // Create task to wait for process exit and closing all output streams
            var processTask = Task.WhenAll(waitForExit, outputCloseEvent.Task, errorCloseEvent.Task);

            // Waits process completion and then checks it was not completed by timeout
            if (await Task.WhenAny(Task.Delay(timeout), processTask) == processTask && waitForExit.Result)
            {
                result.ExitCode = process.ExitCode;
                result.Output = outputBuilder.ToString();
                result.Error = errorBuilder.ToString();
            }
            else
            {
                try
                {
                    // Kill hung process
                    process.Kill();
                }
                catch
                {
                    // ignored
                }
            }
        }

        return result;
    }


    private static Task<bool> WaitForExitAsync(Process process, int timeout)
    {
        return Task.Run(() => process.WaitForExit(timeout));
    }


    public struct ProcessResult
    {
        public int? ExitCode;
        public string Output;
        public string Error;
    }
}

Thanks @georg-jung!

Just wanted to add a few comments since I've found your post:

no handling of ps.Start();

To the best of my knowledge, false can only be returned with shell execute, although I may be wrong. I have never had a false return though so in order to handle it I would need a test that exercises this behavior. Basically I'm waiting for the issue to happen first before solving it.

does many things that are imho out of scope for such a library

Interestingly enough, CliWrap also has all the features of ProcessX, which is the event stream execution model. So you don't have to compromise.

more complicated than ProcessStartAsync (maybe interesting if one plans to pipe binary data/wants to stream output of one process to another)

Same here, CliWrap has a powerful support for piping in which the configuration and execution are also separate.

While they do share features, I liked yours better in terms of separation of concerns and think it's less opinionated, that's what I meant. Like deciding "developers tend to write things to the console instead of an ILogger" (by offering an API for one but not the other) is a thing I considered "out of scope" ;-); but after all that's just my opinion too, I guess. So - keep up the great work!

❤️