c# - 我正在尝试读取 c# 中进程的输出，但收到此消息 "Cannot mix synchronous and asynchronous operation on process stream."

Question

我正在使用 xcopy 编写一个备份程序，因为有很多大文件需要一段时间，所以我想显示进度。当我尝试使用 StreamReader 获取标准输出时，它在调试时出现此错误消息。 “不能在进程流上混契约(Contract)步和异步操作。”

  public void backup_worker_DoWork(object sender, DoWorkEventArgs e)
    {
        int loop = 1;

        backup_worker.WorkerReportsProgress = true;

        Process xcopy = new Process();
        ProcessStartInfo startinfo = new ProcessStartInfo();
        startinfo.CreateNoWindow = true;
        startinfo.UseShellExecute = false;
        startinfo.RedirectStandardError = true;
        startinfo.RedirectStandardOutput = true;
        startinfo.FileName = Environment.CurrentDirectory + "\\xcopy.exe";
        startinfo.Arguments = '"' + source + '"' + " " + '"' + target + '"' + " " + "/s /e /y";
        xcopy.StartInfo.RedirectStandardOutput = true;
        xcopy.StartInfo = startinfo;

        xcopy.Start();
        xcopy.BeginErrorReadLine();
        xcopy.BeginOutputReadLine();

        StreamReader sr = xcopy.StandardOutput;

        while (loop > 0)
        {
            progress = sr.ReadLine();
            output_list.Items.Add(progress);
        }

        xcopy.OutputDataReceived += new DataReceivedEventHandler(backup_worker_OutputDataRecieved);
        xcopy.ErrorDataReceived += new DataReceivedEventHandler(backup_worker_ErrorDataReceived);
        xcopy.WaitForExit();
        backup_worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backup_worker_RunWorkerCompleted);
    }

    void backup_worker_ErrorDataReceived(object sender, DataReceivedEventArgs e)
    {

    }

    void backup_worker_OutputDataRecieved(object sender, DataReceivedEventArgs e)
    {
    }

    void backup_worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        MessageBox.Show("Completed");
    }

请帮忙。提前致谢

Answer 1

问题是您同时使用了同步和异步输出:

// Using async version here...
xcopy.BeginOutputReadLine();


StreamReader sr = xcopy.StandardOutput;

while (loop > 0)
{
    // Trying to use synchronous reading here
    progress = sr.ReadLine();

您需要将算法设计为使用一个选项或另一个选项，但不能同时使用两个选项。