Using AttachConsole, user must hit enter to get regular command line

Here is the safest hack that solves the Enter key problem regardless of whether the console window is in the foreground, background, or minimized. You can even run it in multiple console windows.

using System;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;

namespace WindowsAndConsoleApp
{
  static class Program
  {
    const uint WM_CHAR = 0x0102;
    const int VK_ENTER = 0x0D;

    [DllImport("kernel32.dll")]
    static extern bool AttachConsole(int dwProcessId);
    private const int ATTACH_PARENT_PROCESS = -1;

    [DllImport("kernel32.dll", SetLastError = true)]
    static extern bool FreeConsole();

    [DllImport("kernel32.dll")]
    static extern IntPtr GetConsoleWindow();

    [DllImport("user32.dll")]
    static extern int SendMessage(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);

    [STAThread]
    static void Main(string[] args)
    {
        if (args.Length > 0)
        {
            // Do this first.
            AttachConsole(ATTACH_PARENT_PROCESS);

            Console.Title = "Console Window - Enter Key Test";
            Console.WriteLine("Getting the handle of the currently executing console window...");
            IntPtr cw = GetConsoleWindow();
            Console.WriteLine($"Console handle: {cw.ToInt32()}");
            Console.WriteLine("\nPut some windows in from of this one...");
            Thread.Sleep(5000);
            Console.WriteLine("Take your time...");
            Thread.Sleep(5000);
            Console.WriteLine("Sending the Enter key now...");

            // Send the Enter key to the console window no matter where it is.
            SendMessage(cw, WM_CHAR, (IntPtr)VK_ENTER, IntPtr.Zero);

            // Do this last.
            FreeConsole();
        }
        else
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new MainForm());
        }
    }
  }
}

Try adding this line just before your exe exits...

System.Windows.Forms.SendKeys.SendWait("{ENTER}");

Bit of a hack, but best I could find when I encountered that problem.