Question

我正在使用.NET和C＃来启动进程并异步读取它的输出。我的问题是在我的程序读取输出之前似乎有一段延迟。如果我在命令行上运行可执行文件，它会在开始运行时立即输出。但是当我使用我的代码运行它时，在Process退出之前不会调用ReadOutput事件处理程序。我想使用它来提供进程输出的实时视图，所以我不想等待（几分钟）直到进程退出。

以下是一些相关代码：

MyProcess = new Process();
MyProcess.StartInfo.FileName = command;
MyProcess.StartInfo.Arguments = args;
MyProcess.StartInfo.UseShellExecute = false;
MyProcess.StartInfo.RedirectStandardOutput = true;
MyProcess.StartInfo.RedirectStandardError = true;
MyProcess.StartInfo.RedirectStandardInput = true;
MyProcess.OutputDataReceived += new DataReceivedEventHandler(ReadOutput);
MyProcess.ErrorDataReceived += new DataReceivedEventHandler(ReadOutput);

if (!MyProcess.Start())
{
    throw new Exception("Process could not be started");
}

try
{
    MyProcess.BeginOutputReadLine();
    MyProcess.BeginErrorReadLine();
}
catch (Exception ex)
{
    throw new Exception("Unable to begin asynchronous reading from process";
}

这是我的事件处理程序：

private void ReadOutput(object sendingProcess, DataReceivedEventArgs outLine)
{
    OutputBuilder.AppendLine(outLine.Data);
    Console.WriteLine(outLine.Data);
    Console.Out.Flush();
}

Answer 1

根据我使用lambda语法的注释，这就是我这样做的方式（C＃3）。

    /// <summary>
    /// Collects standard output text from the launched program.
    /// </summary>
    private static readonly StringBuilder outputText = new StringBuilder();

    /// <summary>
    /// Collects standard error text from the launched program.
    /// </summary>
    private static readonly StringBuilder errorText = new StringBuilder();

    /// <summary>
    /// The program's entry point.
    /// </summary>
    /// <param name="args">The command-line arguments.</param>
    /// <returns>The exit code.</returns>
    private static int Main(string[] args)
    {
        using (var process = Process.Start(new ProcessStartInfo(
            "program.exe",
            args)
            {
                CreateNoWindow = true,
                ErrorDialog = false,
                RedirectStandardError = true,
                RedirectStandardOutput = true,
                UseShellExecute = false
            }))
        {
            process.OutputDataReceived += (sendingProcess, outLine) =>
                outputText.AppendLine(outLine.Data);

            process.ErrorDataReceived += (sendingProcess, errorLine) =>
                errorText.AppendLine(errorLine.Data);

            process.BeginOutputReadLine();
            process.BeginErrorReadLine();
            process.WaitForExit();
            Console.WriteLine(errorText.ToString());
            Console.WriteLine(outputText.ToString());
            return process.ExitCode;
        }

Answer 2

您的方法中的问题可能是该进程仅在退出时完成一行的输出。没有办法控制异步事件处理程序何时触发。

在控制台应用程序中，最好的办法是定期检查新输出并同步读取和显示：

        while (!p.HasExited)
        {
            if (!p.StandardOutput.EndOfStream)
            {
                errorBuilder.Append(p.StandardError.ReadToEnd());
                outputBuilder.Append(p.StandardOutput.ReadToEnd());
                Console.Write(p.StandardOutput);
            }
            else
            {
                Thread.Sleep(200);
            }
        }

在UI项目中，您分别对WinForms和WPF使用Timer或DispatcherTimer来调用循环内容并更新UI。

请注意，我不会刷新Console.Out，因为Console.Write()和Console.WriteLine()会自动导致此问题。

Answer 3

尝试添加MyProcess.WaitForExit方法调用：

MyProcess.BeginOutputReadLine();
MyProcess.BeginErrorReadLine();

// will wait for the associated process to exit
MyProcess.WaitForExit();

异步读取过程输出时延迟

3 个答案: