Redirect WriteFile func writes to console

I have a problem with redirect console app output and input. The problem is that any example I found does not work for me. I want to develop WPF GUI for a console app. This is the example code to redirect output:

ProcessStartInfo start = new ProcessStartInfo();
start.FileName = "C:\\myapp.exe"; // Specify exe name.
start.UseShellExecute = false;
start.RedirectStandardOutput = true;
using (Process process = Process.Start(start))
{
    using (StreamReader reader = process.StandardOutput)
    {
        string result = reader.ReadToEnd();
        Console.Write(result);
    }
}

So I did some reverse engineering on the console app and I found that this app is compiled using Microsoft Visual C 6.0. The app uses WriteFile to output to the console and first argument passed to the function equals 7.
I wrote the example code:

#include "stdafx.h"
#include <windows.h>

int main()
{
    AllocConsole();
    HANDLE hStdout;
    HANDLE hStdout2 = (HANDLE)0x00000007;
    char s[] = "Hello world !\r\n";
    char s2[] = "Hello world !CONOUT\r\n";
    char s3[] = "test\r\n";
    DWORD dwBytesWritten;

    HANDLE hScreenBuffer = CreateFileA("CONOUT$", GENERIC_READ | GENERIC_WRITE, FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL);

    hStdout = GetStdHandle(STD_OUTPUT_HANDLE); // hStdout equals 7 after this call
    WriteFile(hStdout2, s3, (DWORD)strlen(s3), &dwBytesWritten, NULL);  //prints always to console 
    WriteFile((HANDLE)0x00000007, s3, (DWORD)strlen(s3), &dwBytesWritten, NULL);    //prints always to console 
    WriteFile(hStdout, s, (DWORD)strlen(s), &dwBytesWritten, NULL);     //can be redirected; example TestCON.exe > test.txt
    WriteFile(hScreenBuffer, s2, (DWORD)strlen(s2), &dwBytesWritten, NULL);//prints always to console 

    FreeConsole();

    return 0;
}

I do not understand why this: WriteFile(hStdout, s, (DWORD)strlen(s), &dwBytesWritten, NULL); (hStdout equals 7 checked by debuger) is redirected using my above example code or TestCON.exe > test.txt but this WriteFile((HANDLE)0x00000007, s3, (DWORD)strlen(s3), &dwBytesWritten, NULL); is printed always on the console.
Any suggestions how can I redirect any output to my GUI app?