AttachConsole() - Console.WriteLine() doesn't work sometimes

Question

I know, that this question has been stated before - but I didn't find any answer.
Let's take this simple example:
static class Program
[DllImport("kernel32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool AttachConsole([MarshalAs(UnmanagedType.U4)] int dwProcessId);
[STAThread]
static void Main()
if (AttachConsole(-1))
Console.WriteLine(@"AttachConsole() succeeded!");
else
MessageBox.Show(@"AttachConsole() failed!");
When I start cmd.exe (For example by Run) - it works - I get "AttachConsole() succeeded".
When I start it in any named window (e.g. Developer Command Prompt) - I get nothing. No console output, no message box. Moreover - when I run Marshal.GetLastWin32Error() - I get 2 (File not found).
Is there any way to lose this problem?

Answer 1

Thanks for the tip. I tried this, I tried also the same procedure for standard error, but I haven't noticed any dfference in the application behavior.
I made some further tests only to confirm my suspition, that the stdout/stderr redirection in console window seems not to be working correctly under Window 7 (probably other versions as well).
Once again some code. First C#, to be compiled as WindowsApplcation with the name app.exe.
using System;
using System.Linq;
using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace WindowsFormsApplication12
internal static class Program
[DllImport("kernel32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool AttachConsole([MarshalAs(UnmanagedType.U4)] int dwProcessId);
[STAThread]
private static void Main(string[] args)
if (AttachConsole(-1))
if (args.Length > 0)
Console.WriteLine(args.Aggregate((x,y) => x + " " + y));
else
MessageBox.Show(@"AttachConsole() failed!");
then the batch file for the testing
@echo off
echo Start
start /wait app App call Start
call :BatchLevel1
start /wait app App call Finito
goto End
:BatchLevel1
echo in BatchLevel1
start /wait app App call Level 1
call :BatchLevel2 > nul 2>&1
echo out BatchLevel1
exit /B 0
:BatchLevel2
echo in BatchLevel2
start /wait app App call Level 2
call :BatchLevel3 > nul 2>&1
echo out BatchLevel2
exit /B 0
:BatchLevel3
echo in BatchLevel3
start /wait app App call Level 3
echo out BatchLevel3
exit /B 0
:end
echo Finito
I used start /wait calls to make the output synchronous.
What I have noticed, is bizzare behavior of console outputs. What at first glance seems to be unpredictable, builds in reality a strange pattern. Here are the outputs of three sequential calls of the batch file:
Start
App call Start
in BatchLevel1
App call Level 1
App call Level 2
App call Level 3
out BatchLevel1
Finito
Start
in BatchLevel1
App call Level 2
App call Level 3
out BatchLevel1
App call Finito
Finito
Start
App call Start
in BatchLevel1
App call Level 1
out BatchLevel1
App call Finito
Finito
The echo outputs from the entry point and level 1 are always and the outputs from level 2 and 3 are never present (as expected). The application seems to ignore the stdout redirection, but not for all calls. I can see some kind of looping - the results
of the 4th call are the same as those from the 1st call, 5th are the same as the 2nd and so on.
Even more interesting is the situation when I remove two stderr redirections (2>&1). When I start a fresh console I can see the "right" output:
Start
App call Start
in BatchLevel1
App call Level 1
out BatchLevel1
App call Finito
Finito
But in the console window when some calls have been already made this output can be another:
Start
in BatchLevel1
App call Level 2
App call Level 3
out BatchLevel1
Finito
What is also interesting to notice, without stderr redirection the batch output is always the same.
I will try to perform some more tests, but for me it seems to be an application error in cmd.exe...