How to set a console application window to be the top most window (C#)?

You can P/Invoke SetWindowPos from the Windows API:

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

class Program
{
    [DllImport("user32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool SetWindowPos(
        IntPtr hWnd, 
        IntPtr hWndInsertAfter, 
        int x, 
        int y, 
        int cx, 
        int cy, 
        int uFlags);

    private const int HWND_TOPMOST = -1;
    private const int SWP_NOMOVE = 0x0002;
    private const int SWP_NOSIZE = 0x0001;

    static void Main(string[] args)
    {
        IntPtr hWnd = Process.GetCurrentProcess().MainWindowHandle;

        SetWindowPos(hWnd, 
            new IntPtr(HWND_TOPMOST), 
            0, 0, 0, 0, 
            SWP_NOMOVE | SWP_NOSIZE);

        Console.ReadKey();
    }
}