Redirect cout from c ++ dll to textbox in c #

Question

I am trying to display the console output (cout) of a method in a dll in a text box in a C # program. Each time I call the method, the console output will be displayed in the Visual Studio output panel. Is there a way to redirect the contents of the output panel to a text box?

The DLL was written by someone else in C ++, and I cannot control it. The DLL is wrapped using SWIG so that it can be called by my C # code.

Answer 1

After the link suggested by David, I decided to write a solution to your problem that is more specific to your case. This version allows you to get standard output in your GUI using the BackgroundWorker PropertyChangedEventHandler callback.

Here is the code for ConsoleRedirector:

 public class ConsoleRedirector : IDisposable { private static ConsoleRedirector _instance; public static void attach(ProgressChangedEventHandler handler, bool forceConsoleRedirection) { Debug.Assert(null == _instance); _instance = new ConsoleRedirector(handler, forceConsoleRedirection); } public static void detatch() { _instance.Dispose(); _instance = null; } public static bool isAttached { get { return null != _instance; } } private static void ResetConsoleOutStream() { //Force console to recreate its output stream the next time Write/WriteLine is called typeof(Console).GetField("_out", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic).SetValue(null, null); } private const int PERIOD = 500; private const int BUFFER_SIZE = 4096; private volatile bool _isDisposed; private BackgroundWorker _worker; private readonly IntPtr _stdout; private readonly Mutex _sync; private readonly System.Threading.Timer _timer; private readonly char[] _buffer; private readonly AnonymousPipeServerStream _outServer; private readonly TextReader _outClient; private readonly bool _forceConsoleRedirection; private StreamWriter _consoleStandardOut; private ConsoleRedirector(ProgressChangedEventHandler handler, bool forceConsoleRedirection) { bool ret; _forceConsoleRedirection = forceConsoleRedirection; if (!_forceConsoleRedirection) { //Make sure Console._out is initialized before we redirect stdout, so the redirection won't affect it TextWriter temp = Console.Out; } AnonymousPipeClientStream client; _worker = new BackgroundWorker(); _worker.ProgressChanged += handler; _worker.DoWork += _worker_DoWork; _worker.WorkerReportsProgress = true; _stdout = GetStdHandle(STD_OUTPUT_HANDLE); _sync = new Mutex(); _buffer = new char[BUFFER_SIZE]; _outServer = new AnonymousPipeServerStream(PipeDirection.Out); client = new AnonymousPipeClientStream(PipeDirection.In, _outServer.ClientSafePipeHandle); Debug.Assert(_outServer.IsConnected); _outClient = new StreamReader(client, Encoding.Default); ret = SetStdHandle(STD_OUTPUT_HANDLE, _outServer.SafePipeHandle.DangerousGetHandle()); Debug.Assert(ret); if (_forceConsoleRedirection) { ResetConsoleOutStream(); //calls to Console.Write/WriteLine will now get made against the redirected stream } _worker.RunWorkerAsync(_outClient); _timer = new System.Threading.Timer(flush, null, PERIOD, PERIOD); } void _worker_DoWork(object sender, DoWorkEventArgs e) { BackgroundWorker worker = (BackgroundWorker)sender; TextReader client = (TextReader)e.Argument; try { while (true) { int read = client.Read(_buffer, 0, BUFFER_SIZE); if (read > 0) worker.ReportProgress(0, new string(_buffer, 0, read)); } } catch (ObjectDisposedException) { // Pipe was closed... terminate } catch (Exception ex) { } } private void flush(object state) { _outServer.Flush(); } public void Dispose() { Dispose(true); } ~ConsoleRedirector() { Dispose(false); } private void Dispose(bool disposing) { if (!_isDisposed) { lock (_sync) { if (!_isDisposed) { _isDisposed = true; _timer.Change(Timeout.Infinite, Timeout.Infinite); _timer.Dispose(); flush(null); try { SetStdHandle(STD_OUTPUT_HANDLE, _stdout);} catch (Exception) { } _outClient.Dispose(); _outServer.Dispose(); if (_forceConsoleRedirection) { ResetConsoleOutStream(); //Calls to Console.Write/WriteLine will now get redirected to the original stdout stream } } } } } private const int STD_OUTPUT_HANDLE = -11; [DllImport("kernel32.dll")] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool SetStdHandle(int nStdHandle, IntPtr hHandle); [DllImport("kernel32.dll")] private static extern IntPtr GetStdHandle(int nStdHandle); } 

Here's a link to the full sample form, which demonstrates how to use it: ConsoleRedirector console form example