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I am trying to read the output of a process in C #, but I get this message "Cannot mix synchronous and asynchronous operation with process thread".

I am writing a backup program using xcopy, and because it requires a large number of large files, so I want to show the progress. When I try to use StreamReader to get standard output, it has this debug error message. "It is not possible to mix synchronous and asynchronous operation with a process thread."

  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");
    }

Please, help. thanks in advance

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3 answers

The problem is that you are using synchronous and asynchronous output:

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


StreamReader sr = xcopy.StandardOutput;

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

, .

+7

MSDN ,

. , . , BeginErrorReadLine ReadLine StandardError . , . , BeginErrorReadLine, ReadLine StandardOutput.



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

        // This should ideally not be in the DoWork, but where you setup or create the worker
        backup_worker.WorkerReportsProgress = true;
        backup_worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backup_worker_RunWorkerCompleted);
        backup_worker.WorkerSupportsCancellation = true;

        // setup your scopy 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 = "/s /e /y " + '"' + source + '"' + " " + '"' + target + '"' + " ";
        Process xcopy = new Process();
        xcopy.StartInfo = startinfo;
        xcopy.ErrorDataReceived += new DataReceivedEventHandler(backup_worker_ErrorDataReceived);

        // start the xcopy and read the output
        xcopy.Start();
        xcopy.BeginErrorReadLine();

        string copiedFileName;
        while ((copiedFileName = xcopy.StandardOutput.ReadLine()) != null) {
            output_list.Items.Add(copiedFileName);
        }

        // we should be done when here, but doesen't hurt to wait
        xcopy.WaitForExit();
    }

    void backup_worker_ErrorDataReceived(object sender, DataReceivedEventArgs e) {
        MessageBox.Show("We have a problem. Figure what needs to be done here!");
    }

    void backup_worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        if (e.Cancelled == true) {
            MessageBox.Show("Canceled!");
        } else if (e.Error != null) {
            MessageBox.Show("Error: " + e.Error.Message);
        } else {
            MessageBox.Show("Completed!");
        }
    }
+4

,

xcopy.BeginOutputReadLine()

use

string s = xcopy.StandardOutput.ReadToEnd()

it should be warned that if you do this both for inference and for error, and one of them is too long, you may be at a standstill.

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