procStartInfo.RedirectStandardOutput not working properly?

Question

procStartInfo.RedirectStandardOutput not working properly i don't know why?
my code:
ProcessStartInfo procStartInfo = new ProcessStartInfo("cmd", "/q /c " + batchFile);
procStartInfo.RedirectStandardOutput = true;

                procStartInfo.RedirectStandardError = true;
                procStartInfo.UseShellExecute = false;
                procStartInfo.CreateNoWindow = true;

                Process proc = new Process();
                proc.StartInfo = procStartInfo;
                proc.StartInfo.CreateNoWindow = true;
                proc.Start();
                string result_prog = proc.StandardOutput.ReadToEnd(); // get result null

Answer 1

Here is an example that may help with whatever you are attempting. The code assumes PowerShell is in the path, gets the IP address without showing a window to a text file and reads back the results once the PowerShell code finishes executing using a language extension.

This method will keep a windows form responsive and if this is not needed process.WaitForExit can be used.

public static class Extensions
{
    public static Task WaitForExitAsync(this Process process, CancellationToken cancellationToken = default)
    {
        if (process.HasExited)
        {
            return Task.CompletedTask;
        }

        var tcs = new TaskCompletionSource<object>();

        process.EnableRaisingEvents = true;
        process.Exited += (sender, args) => tcs.TrySetResult(null);

        if (cancellationToken != default)
        {
            cancellationToken.Register(() => tcs.SetCanceled());
        }

        return process.HasExited ? Task.CompletedTask : tcs.Task;
    }
}

Form code

private async void button1_Click(object sender, EventArgs e)
{
    PowerShellScriptExecute();
}
private string _fileName = "ipPower.txt";
public async void PowerShellScriptExecute()
{
    var start = new ProcessStartInfo
    {
        FileName = "powershell.exe",
        UseShellExecute = false,
        RedirectStandardOutput = true,
        Arguments = "Invoke-RestMethod ipinfo.io/ip", 
        CreateNoWindow = true
    };

    using var process = Process.Start(start);
    using var reader = process.StandardOutput;

    process.EnableRaisingEvents = true;

    var ipAddressResult = reader.ReadToEnd();

    await File.WriteAllTextAsync(_fileName, ipAddressResult);
    await process.WaitForExitAsync();

    Debug.WriteLine(await File.ReadAllTextAsync(_fileName));
}

Answer 2

Please try if this code works for you:

            string file = @"D:\test\txt\test.bat";  
            var process = new Process();  
            var startinfo = new ProcessStartInfo(file);  
            startinfo.RedirectStandardOutput = true;  
            startinfo.UseShellExecute = false;  
            process.StartInfo = startinfo;  
  
            process.OutputDataReceived += (sender, argsx) => Console.WriteLine(argsx.Data);   
            process.Start();  
            process.BeginOutputReadLine();  
            process.WaitForExit();  

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