The .NET Developer's Guide to Windows Security

Chapter 72. How to Programmatically Lock the Console

Have you ever configured your screensaver to require a password or, on Windows XP, to “show the Welcome screen”? I've seen some special-purpose programs that need to implement similar behavior: locking the interactive console under certain conditions. It's easy to do, so I've included it here. The function you need to call is in Win32, and it's called LockWorkstation. Here's a C# program that locks the console when run:

using System.Runtime.InteropServices;

class LockItUp {
  static void Main() {
    LockWorkStation();
  }
  [DllImport("user32.dll")]
  static extern void LockWorkStation();
}

After this program runs, the default desktop will be hidden and the Winlogon desktop will be displayed. All programs ...