Get Live output from Process

To correctly handle output and/or error redirection you must also redirect input. It seem to be feature/bug in runtime of the external application youre starting and from what I have seen so far, it is not mentioned anywhere else.

Example usage:

        Process p = new Process(...);

        p.StartInfo.UseShellExecute = false;
        p.StartInfo.RedirectStandardOutput = true;
        p.StartInfo.RedirectStandardError = true;
        p.StartInfo.RedirectStandardInput = true; // Is a MUST!
        p.EnableRaisingEvents = true;

        p.OutputDataReceived += OutputDataReceived;
        p.ErrorDataReceived += ErrorDataReceived;

        Process.Start();

        p.BeginOutputReadLine();
        p.BeginErrorReadLine();

        p.WaitForExit();

        p.OutputDataReceived -= OutputDataReceived;
        p.ErrorDataReceived -= ErrorDataReceived;

...

    void OutputDataReceived(object sender, DataReceivedEventArgs e)
    {
        // Process line provided in e.Data
    }

    void ErrorDataReceived(object sender, DataReceivedEventArgs e)
    {
        // Process line provided in e.Data
    }

Take a look at this page, it looks this is the solution for you: http://msdn.microsoft.com/en-us/library/system.diagnostics.process.beginoutputreadline.aspx and http://msdn.microsoft.com/en-us/library/system.diagnostics.process.standardoutput.aspx

[Edit] This is a working example:

        Process p = new Process();
        p.StartInfo.RedirectStandardError = true;
        p.StartInfo.RedirectStandardOutput = true;
        p.StartInfo.UseShellExecute = false;
        p.StartInfo.CreateNoWindow = true;
        p.StartInfo.FileName = @"C:\Program Files (x86)\gnuwin32\bin\ls.exe";
        p.StartInfo.Arguments = "-R C:\\";

        p.OutputDataReceived += new DataReceivedEventHandler((s, e) => 
        { 
            Console.WriteLine(e.Data); 
        });
        p.ErrorDataReceived += new DataReceivedEventHandler((s, e) =>
        {
            Console.WriteLine(e.Data);
        });

        p.Start();
        p.BeginOutputReadLine();
        p.BeginErrorReadLine();

Btw, ls -R C:\ lists all files from the root of C: recursively. These are a lot of files, and I'm sure it isn't done when the first results show up in the screen. There is a possibility 7zip holds the output before showing it. I'm not sure what params you give to the proces.