Redirect console output to textbox in separate program

Question

I'm developing an Windows Forms application that requires me to call a separate program to perform a task. The program is a console application and I need to redirect standard output from the console to a TextBox in my program.

I have no problem executing the program from my application, but I don't know how to redirect the output to my application. I need to capture output while the program is running using events.

The console program isn't meant to stop running until my application stops and the text changes constantly at random intervals. What I'm attempting to do is simply hook output from the console to trigger an event handler which can then be used to update the TextBox.

I am using C# to code the program and using the .NET framework for development. The original application is not a .NET program.

EDIT: Here's example code of what I'm trying to do. In my final app, I'll replace Console.WriteLine with code to update the TextBox. I tried to set a breakpoint in my event handler, and it isn't even reached.

    void Method()
    {
        var p = new Process();
        var path = @"C:\ConsoleApp.exe";

        p.StartInfo.FileName = path;
        p.StartInfo.UseShellExecute = false;
        p.OutputDataReceived += p_OutputDataReceived;

        p.Start();
    }

    static void p_OutputDataReceived(object sender, DataReceivedEventArgs e)
    {
        Console.WriteLine(">>> {0}", e.Data);
    }

Answer 1

This works for me:

void RunWithRedirect(string cmdPath)
{
    var proc = new Process();
    proc.StartInfo.FileName = cmdPath;

    // set up output redirection
    proc.StartInfo.RedirectStandardOutput = true;
    proc.StartInfo.RedirectStandardError = true;    
    proc.EnableRaisingEvents = true;
    proc.StartInfo.CreateNoWindow = true;
    // see below for output handler
    proc.ErrorDataReceived += proc_DataReceived;
    proc.OutputDataReceived += proc_DataReceived;

    proc.Start();

    proc.BeginErrorReadLine();
    proc.BeginOutputReadLine();

    proc.WaitForExit();
}

void proc_DataReceived(object sender, DataReceivedEventArgs e)
{
    // output will be in string e.Data
}

Answer 2

You can use the following code

        MemoryStream mem = new MemoryStream(1000);
        StreamWriter writer = new StreamWriter(mem);
        Console.SetOut(writer);

        Assembly assembly = Assembly.LoadFrom(@"C:\ConsoleApp.exe");
        assembly.EntryPoint.Invoke(null, null);
        writer.Close();

        string s = Encoding.Default.GetString(mem.ToArray());
        mem.Close();

Answer 3

See http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/72cf626c-92c1-4988-b559-39b91a173181/.

Answer 4

I've added a number of helper methods to the O2 Platform (Open Source project) which allow you easily script an interaction with another process via the console output and input (see http://code.google.com/p/o2platform/source/browse/trunk/O2_Scripts/APIs/Windows/CmdExe/CmdExeAPI.cs)

Also useful for you might be the API that allows the viewing of the console output of the current process (in an existing control or popup window). See this blog post for more details: http://o2platform.wordpress.com/2011/11/26/api_consoleout-cs-inprocess-capture-of-the-console-output/ (this blog also contains details of how to consume the console output of new processes)

Answer 5

Thanks to Marc Maxham for his answer that save me time !

As Jon of All Trades notice it, UseShellExecute must be set to false in order to redirect IO streams, otherwise the Start() call throws an InvalidOperationException.

Here is my modification of the code where txtOut is a WPF readonly Textbox

void RunWithRedirect(string cmdargs)
{
    var proc = new Process()
    {
        StartInfo = new ProcessStartInfo("cmd.exe", "/k " + cmdargs)
        {
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            CreateNoWindow = true
        },
        EnableRaisingEvents = true
    };

    // see below for output handler
    proc.ErrorDataReceived += proc_DataReceived;
    proc.OutputDataReceived += proc_DataReceived;
    proc.Start();

    proc.BeginErrorReadLine();
    proc.BeginOutputReadLine();

    proc.WaitForExit();
}

void proc_DataReceived(object sender, DataReceivedEventArgs e)
{
    if (e.Data != null)
        Dispatcher.BeginInvoke(new Action( () => txtOut.Text += (Environment.NewLine + e.Data) ));
}