Process.Startに相当する非同期機能はありますか？

Question

タイトルが示すように、Process.Start（別のアプリケーションまたはバッチファイルを実行できます）に相当するものがありますか？

私は小さなコンソールアプリで遊んでいますが、これはasyncとawaitを使用するのに最適な場所のように思えましたが、このシナリオに関するドキュメントは見つかりません。

私が考えているのは、これらの線に沿ったものです：

void async RunCommand()
{
    var result = await Process.RunAsync("command to run");
}

Answer 1

Process.Start()はプロセスを開始するだけで、終了するまで待機しないため、asyncにすることはあまり意味がありません。それでもやりたい場合は、await Task.Run(() => Process.Start(fileName))のようなことができます。

ただし、プロセスが完了するまで非同期で待機する場合は、 Exitedイベント と TaskCompletionSource を併用できます。

static Task<int> RunProcessAsync(string fileName)
{
    var tcs = new TaskCompletionSource<int>();

    var process = new Process
    {
        StartInfo = { FileName = fileName },
        EnableRaisingEvents = true
    };

    process.Exited += (sender, args) =>
    {
        tcs.SetResult(process.ExitCode);
        process.Dispose();
    };

    process.Start();

    return tcs.Task;
}

Answer 2

svickの答え に基づいた私の見解を以下に示します。出力のリダイレクト、終了コードの保持、およびエラー処理のわずかな改善（開始できなかった場合でもProcessオブジェクトを破棄する）を追加します。

public static async Task<int> RunProcessAsync(string fileName, string args)
{
    using (var process = new Process
    {
        StartInfo =
        {
            FileName = fileName, Arguments = args,
            UseShellExecute = false, CreateNoWindow = true,
            RedirectStandardOutput = true, RedirectStandardError = true
        },
        EnableRaisingEvents = true
    })
    {
        return await RunProcessAsync(process).ConfigureAwait(false);
    }
}    
private static Task<int> RunProcessAsync(Process process)
{
    var tcs = new TaskCompletionSource<int>();

    process.Exited += (s, ea) => tcs.SetResult(process.ExitCode);
    process.OutputDataReceived += (s, ea) => Console.WriteLine(ea.Data);
    process.ErrorDataReceived += (s, ea) => Console.WriteLine("ERR: " + ea.Data);

    bool started = process.Start();
    if (!started)
    {
        //you may allow for the process to be re-used (started = false) 
        //but I'm not sure about the guarantees of the Exited event in such a case
        throw new InvalidOperationException("Could not start process: " + process);
    }

    process.BeginOutputReadLine();
    process.BeginErrorReadLine();

    return tcs.Task;
}

Answer 3

別のアプローチがあります。 svick および Ohad's の回答に似た概念ですが、Processタイプで拡張メソッドを使用します。

拡張方法：

public static Task RunAsync(this Process process)
{
    var tcs = new TaskCompletionSource<object>();
    process.EnableRaisingEvents = true;
    process.Exited += (s, e) => tcs.TrySetResult(null);
    // not sure on best way to handle false being returned
    if (!process.Start()) tcs.SetException(new Exception("Failed to start process."));
    return tcs.Task;
}

包含メソッドの使用例：

public async Task ExecuteAsync(string executablePath)
{
    using (var process = new Process())
    {
        // configure process
        process.StartInfo.FileName = executablePath;
        process.StartInfo.UseShellExecute = false;
        process.StartInfo.CreateNoWindow = true;
        // run process asynchronously
        await process.RunAsync();
        // do stuff with results
        Console.WriteLine($"Process finished running at {process.ExitTime} with exit code {process.ExitCode}");
    };// dispose process
}

Answer 4

プロセスを開始するためのクラスを作成しましたが、さまざまな要件のために、ここ数年で成長していました。使用中に、ExitCodeを破棄し、読み取ることで、Processクラスにいくつかの問題が見つかりました。クラスによって処理され、コードコメントとして言及されます。

このクラスにはいくつかの可能性があります。たとえば、出力の読み取り、管理者または別のユーザーとしての開始、例外のキャッチ、この非同期のすべての開始などです。キャンセル。実行中に出力を読み取ることもできます。

public class ProcessSettings
{
    public string FileName { get; set; }
    public string Arguments { get; set; } = "";
    public string WorkingDirectory { get; set; } = "";
    public string InputText { get; set; } = null;
    public int Timeout_milliseconds { get; set; } = -1;
    public bool ReadOutput { get; set; }
    public bool ShowWindow { get; set; }
    public bool KeepWindowOpen { get; set; }
    public bool StartAsAdministrator { get; set; }
    public string StartAsUsername { get; set; }
    public string StartAsUsername_Password { get; set; }
    public string StartAsUsername_Domain { get; set; }
    public bool DontReadExitCode { get; set; }
    public CancellationToken CancellationToken { get; set; }
}

public class ProcessOutputReader   // Optional, to get the output while executing instead only as result at the end
{
    public event TextEventHandler OutputChanged;
    public event TextEventHandler OutputErrorChanged;
    public void UpdateOutput(string text)
    {
        OutputChanged?.Invoke(this, new TextEventArgs(text));
    }
    public void UpdateOutputError(string text)
    {
        OutputErrorChanged?.Invoke(this, new TextEventArgs(text));
    }
    public delegate void TextEventHandler(object sender, TextEventArgs e);
    public class TextEventArgs : EventArgs
    {
        public string Text { get; }
        public TextEventArgs(string text) { Text = text; }
    }
}

public class ProcessResult
{
    public string Output { get; set; }
    public string OutputError { get; set; }
    public int ExitCode { get; set; }
    public bool WasCancelled { get; set; }
    public bool WasSuccessful { get; set; }
}

public class ProcessStarter
{
    public ProcessResult Execute(ProcessSettings settings, ProcessOutputReader outputReader = null)
    {
        return Task.Run(() => ExecuteAsync(settings, outputReader)).GetAwaiter().GetResult();
    }

    public async Task<ProcessResult> ExecuteAsync(ProcessSettings settings, ProcessOutputReader outputReader = null)
    {
        if (settings.FileName == null) throw new ArgumentNullException(nameof(ProcessSettings.FileName));
        if (settings.Arguments == null) throw new ArgumentNullException(nameof(ProcessSettings.Arguments));

        var cmdSwitches = "/Q " + (settings.KeepWindowOpen ? "/K" : "/C");

        var arguments = $"{cmdSwitches} {settings.FileName} {settings.Arguments}";
        var startInfo = new ProcessStartInfo("cmd", arguments)
        {
            UseShellExecute = false,
            RedirectStandardOutput = settings.ReadOutput,
            RedirectStandardError = settings.ReadOutput,
            RedirectStandardInput = settings.InputText != null,
            CreateNoWindow = !(settings.ShowWindow || settings.KeepWindowOpen),
        };
        if (!string.IsNullOrWhiteSpace(settings.StartAsUsername))
        {
            if (string.IsNullOrWhiteSpace(settings.StartAsUsername_Password))
                throw new ArgumentNullException(nameof(ProcessSettings.StartAsUsername_Password));
            if (string.IsNullOrWhiteSpace(settings.StartAsUsername_Domain))
                throw new ArgumentNullException(nameof(ProcessSettings.StartAsUsername_Domain));
            if (string.IsNullOrWhiteSpace(settings.WorkingDirectory))
                settings.WorkingDirectory = Path.GetPathRoot(Path.GetTempPath());

            startInfo.UserName = settings.StartAsUsername;
            startInfo.PasswordInClearText = settings.StartAsUsername_Password;
            startInfo.Domain = settings.StartAsUsername_Domain;
        }
        var output = new StringBuilder();
        var error = new StringBuilder();
        if (!settings.ReadOutput)
        {
            output.AppendLine($"Enable {nameof(ProcessSettings.ReadOutput)} to get Output");
        }
        if (settings.StartAsAdministrator)
        {
            startInfo.Verb = "runas";
            startInfo.UseShellExecute = true;  // Verb="runas" only possible with ShellExecute=true.
            startInfo.RedirectStandardOutput = startInfo.RedirectStandardError = startInfo.RedirectStandardInput = false;
            output.AppendLine("Output couldn't be read when started as Administrator");
        }
        if (!string.IsNullOrWhiteSpace(settings.WorkingDirectory))
        {
            startInfo.WorkingDirectory = settings.WorkingDirectory;
        }
        var result = new ProcessResult();
        var taskCompletionSourceProcess = new TaskCompletionSource<bool>();

        var process = new Process { StartInfo = startInfo, EnableRaisingEvents = true };
        try
        {
            process.OutputDataReceived += (sender, e) =>
            {
                if (e?.Data != null)
                {
                    output.AppendLine(e.Data);
                    outputReader?.UpdateOutput(e.Data);
                }
            };
            process.ErrorDataReceived += (sender, e) =>
            {
                if (e?.Data != null)
                {
                    error.AppendLine(e.Data);
                    outputReader?.UpdateOutputError(e.Data);
                }
            };
            process.Exited += (sender, e) =>
            {
                try { (sender as Process)?.WaitForExit(); } catch (InvalidOperationException) { }
                taskCompletionSourceProcess.TrySetResult(false);
            };

            try
            {
                process.Start();
            }
            catch (System.ComponentModel.Win32Exception ex)
            {
                if (ex.NativeErrorCode == 1223)
                {
                    error.AppendLine("AdminRights request Cancelled by User!! " + ex);
                    taskCompletionSourceProcess.SetException(ex);
                }
                else
                {
                    error.AppendLine("Win32Exception thrown: " + ex);
                    taskCompletionSourceProcess.SetException(ex);
                }
            }
            catch (Exception ex)
            {
                error.AppendLine("Exception thrown: " + ex);
                taskCompletionSourceProcess.SetException(ex);
            }
            if (success && startInfo.RedirectStandardOutput)
                process.BeginOutputReadLine();
            if (success && startInfo.RedirectStandardError)
                process.BeginErrorReadLine();
            if (success && startInfo.RedirectStandardInput)
            {
                var writeInputTask = Task.Factory.StartNew(() => WriteInputTask());
            }

            async void WriteInputTask()
            {
                var processRunning = true;
                await Task.Delay(50).ConfigureAwait(false);
                try { processRunning = !process.HasExited; } catch { }
                while (processRunning)
                {
                    if (settings.InputText != null)
                    {
                        try
                        {
                            await process.StandardInput.WriteLineAsync(settings.InputText).ConfigureAwait(false);
                            await process.StandardInput.FlushAsync().ConfigureAwait(false);
                            settings.InputText = null;
                        }
                        catch { }
                    }
                    await Task.Delay(5).ConfigureAwait(false);
                    try { processRunning = !process.HasExited; } catch { processRunning = false; }
                }
            }

            if (success && settings.CancellationToken != default(CancellationToken))
                settings.CancellationToken.Register(() => taskCompletionSourceProcess.TrySetResult(true));
            if (success && settings.Timeout_milliseconds > 0)
                new CancellationTokenSource(settings.Timeout_milliseconds).Token.Register(() => taskCompletionSourceProcess.TrySetResult(true));

            var taskProcess = taskCompletionSourceProcess.Task;
            await taskProcess.ConfigureAwait(false);
            if (taskProcess.Result == true) // process was cancelled by token or timeout
            {
                if (!process.HasExited)
                {
                    result.WasCancelled = true;
                    error.AppendLine("Process was cancelled!");
                    try
                    {
                        process.CloseMainWindow();
                        await Task.Delay(30).ConfigureAwait(false);
                        if (!process.HasExited)
                        {
                            process.Kill();
                        }
                    }
                    catch { }
                }
            }
            result.ExitCode = settings.DontReadExitCode ? -1 : process.ExitCode;     // Reason: sometimes, like when timeout /t 30 is started, reading the ExitCode is only possible if the timeout expired, even if process.Kill was called before.
            process.Close();
        }
        finally { var disposeTask = Task.Factory.StartNew(() => process.Dispose()); }    // start in new Task because disposing sometimes waits until the process is finished, for example while executing following command: ping -n 30 -w 1000 127.0.0.1 > nul
        if (result.ExitCode == -1073741510 && !result.WasCancelled)
        {
            error.AppendLine($"Process exited by user!");
        }
        result.WasSuccessful = !result.WasCancelled && result.ExitCode == 0;
        result.Output = output.ToString();
        result.OutputError = error.ToString();
        return result;
    }
}

Answer 5

私はプロセスの廃棄について本当に心配しています、出口非同期を待つのはどうですか？これは私の提案です（前に基づいています）：

public static class ProcessExtensions
{
    public static Task WaitForExitAsync(this Process process)
    {
        var tcs = new TaskCompletionSource<object>();
        process.EnableRaisingEvents = true;
        process.Exited += (s, e) => tcs.TrySetResult(null);
        return process.HasExited ? Task.CompletedTask : tcs.Task;
    }        
}

次に、次のように使用します。

public static async Task<int> ExecAsync(string command, string args)
{
    ProcessStartInfo psi = new ProcessStartInfo();
    psi.FileName = command;
    psi.Arguments = args;

    using (Process proc = Process.Start(psi))
    {
        await proc.WaitForExitAsync();
        return proc.ExitCode;
    }
}