Although its rare but at times while building desktop based applications, we might come across situation wherein we are asked to handle “Screen Saver” operation i.e. perform some logic based on whether the “Screen Saver” is on of off. I found the following code snippet on internet almost two years back. I would like to thank the original author of the code. It’s been long time and its not possible for me to search for the original author of the code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace SystemEvent
{
    public static class NativeMethods
    {
        // Used to check if the screen saver is running
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool SystemParametersInfo(uint uAction,
                                                       uint uParam,
                                                       ref bool lpvParam,
                                                       int fWinIni);

        // Used to check if the workstation is locked
        [DllImport("user32", SetLastError = true)]
        private static extern IntPtr OpenDesktop(string lpszDesktop,
                                                 uint dwFlags,
                                                 bool fInherit,
                                                 uint dwDesiredAccess);

        [DllImport("user32", SetLastError = true)]
        private static extern IntPtr OpenInputDesktop(uint dwFlags,
                                                      bool fInherit,
                                                      uint dwDesiredAccess);

        [DllImport("user32", SetLastError = true)]
        private static extern IntPtr CloseDesktop(IntPtr hDesktop);

        [DllImport("user32", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool SwitchDesktop(IntPtr hDesktop);

        // Check if the workstation has been locked.
        public static bool IsWorkstationLocked()
        {
            const int DESKTOP_SWITCHDESKTOP = 256;
            IntPtr hwnd = OpenInputDesktop(0, false, DESKTOP_SWITCHDESKTOP);

            if (hwnd == IntPtr.Zero)
            {
                // Could not get the input desktop, might be locked already?
                hwnd = OpenDesktop("Default", 0, false, DESKTOP_SWITCHDESKTOP);
            }

            // Can we switch the desktop?
            if (hwnd != IntPtr.Zero)
            {
                if (SwitchDesktop(hwnd))
                {
                    // Workstation is NOT LOCKED.
                    CloseDesktop(hwnd);
                }
                else
                {
                    CloseDesktop(hwnd);
                    // Workstation is LOCKED.
                    return true;
                }
            }

            return false;
        }

        // Check if the screensaver is busy running.
        public static bool IsScreensaverRunning()
        {
            const int SPI_GETSCREENSAVERRUNNING = 114;
            bool isRunning = false;

            if (!SystemParametersInfo(SPI_GETSCREENSAVERRUNNING, 0, ref isRunning, 0))
            {
                // Could not detect screen saver status...
                return false;
            }

            if (isRunning)
            {
                // Screen saver is ON.
                return true;
            }

            // Screen saver is OFF.
            return false;
        }
    }
}