Данный пример демонстрирует возможность запуска Windows Form приложения в либо режиме консоли (консольное окно)

либо как как обычное Windows Form приложение.

using System;
using System.IO;
using System.Runtime.InteropServices;
 
namespace FormConsole
{
      public class ConsoleOUT : IDisposable
      {
            //
            // Импортируем фнкции из kernel32.dll
            //
            [DllImport("kernel32.dll", SetLastError=true)]
            protected static extern bool AllocConsole();
 
            [DllImport("kernel32.dll", SetLastError=false)]
            protected static extern bool FreeConsole();
 
            [DllImport("kernel32.dll", SetLastError=true)]
            protected static extern IntPtr GetStdHandle( int nStdHandle );
 
            [DllImport("kernel32.dll", SetLastError=true)]
            protected static extern bool SetStdHandle( int nStdHandle, 
                            IntPtr hConsoleOutput );
 
            [DllImport("kernel32.dll", CharSet=CharSet.Auto, SetLastError=true)]
            protected static extern IntPtr CreateFile(
                  string  fileName,
                  int   desiredAccess,
                  int   shareMode,
                  IntPtr  securityAttributes,
                  int   creationDisposition,
                  int   flagsAndAttributes,
                  IntPtr  templateFile );
 
            [DllImport("kernel32.dll", ExactSpelling=true, SetLastError=true)]
            protected static extern bool CloseHandle( IntPtr handle );
 
            
            private static IntPtr conOut;
            private static IntPtr oldOut;
 
            /// <summary>
            /// ConsoleOUT
            /// </summary>
            public ConsoleOUT()
            {
                  if (oldOut == IntPtr.Zero)
                        oldOut = GetStdHandle( -11 );
 
                  if (!AllocConsole())
                        throw new Exception("AllocConsole");
 
                  conOut = CreateFile( "CONOUT$", 0x40000000, 2, 
                                 IntPtr.Zero, 3, 0, IntPtr.Zero );
 
                  if (!SetStdHandle(-11, conOut))
                        throw new Exception("SetStdHandle");
 
                  Stream standard = Console.OpenStandardOutput();
                  StreamWriter writer = new StreamWriter(standard);
                  writer.AutoFlush = true;
                  //
                  Console.SetOut(writer);
                  Console.SetError(writer);
            }
 
            /// <summary>
            /// Dispose
            /// </summary>
            public void Dispose()
            {
                  if (! CloseHandle(conOut))
                        throw new Exception("CloseHandle");
                  conOut = IntPtr.Zero;
                  if (! FreeConsole())
                        throw new Exception("FreeConsole");
                  if (!SetStdHandle(-11, oldOut))
                        throw new Exception("SetStdHandle");
            }
 
      }
}