Service needs to detect if workstation is locked, and screen saver is active

Question

I\'m working on a service that needs to detect user states for all user(s) logged on to a single machine. Specifically, I want to check to see whether or not the screen save

Answer 1

The most straightforward way would be to have a small app running in each user's session. Each instance of this app could communicate with the main instance of the service.

Windows tries pretty hard to keep logon sessions separate -- both between services and the interactive desktop, and between individual Terminal Services sessions -- so it gets very tricky to access this sort of information about a user's session unless your app is running in that session to begin with.

Answer 2

As a serivce you can use the event OnSessionChange to catch all your relevant moments.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceProcess;
using System.Diagnostics;

namespace MyCode
{
    class MyService : ServiceBase
    {
        public MyService()
        {
            this.CanHandleSessionChangeEvent = true;
        }

        protected override void OnSessionChange(SessionChangeDescription changeDescription)
        {
            switch (changeDescription.Reason)
            {
                case SessionChangeReason.SessionLogon:
                    Debug.WriteLine(changeDescription.SessionId + " logon");
                    break;
                case SessionChangeReason.SessionLogoff:
                    Debug.WriteLine(changeDescription.SessionId + " logoff");
                    break;
                case SessionChangeReason.SessionLock:
                    Debug.WriteLine(changeDescription.SessionId + " lock");
                    break;
                case SessionChangeReason.SessionUnlock:
                    Debug.WriteLine(changeDescription.SessionId + " unlock");
                    break;
            }

            base.OnSessionChange(changeDescription);
        }
    }
}

I'm sure it is possible to identify the user based on changeDescription.SessionId. But at the moment i don't know how...

EDIT: This should be a possibilty

    public static WindowsIdentity GetUserName(int sessionId)
    {
        foreach (Process p in Process.GetProcesses())
        {
            if(p.SessionId == sessionId) {                    
                return new WindowsIdentity(p.Handle);                          
            }                
        }
        return null;
    }

MSDN Links

• system.serviceprocess.servicebase.onsessionchange
• system.serviceprocess.sessionchangedescription
• system.serviceprocess.sessionchangereason

Answer 3

A simpler solution would be to use Cassia, which wraps the various TS APIs, to check how long users have been idle for:

using Cassia;

foreach (ITerminalServicesSession session in new TerminalServicesManager().GetSessions())
{
    if ((session.CurrentTime - session.LastInputTime > TimeSpan.FromMinutes(10)) &&
        (!string.IsNullOrEmpty(session.UserName)))
    {
        Console.WriteLine("Session {0} (User {1}) is idle", session.SessionId, session.UserName);
    }
}