Determining if a local user account is logged into Windows.

using System;
using System.Diagnostics;
using System.Linq;
using System.Windows.Forms;

namespace UserLoginChecker
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void MainForm_Load(object sender, EventArgs e)
        {
            popUserList();
        }

        private void popUserList()
        {
            userAccountLst.Items.Clear();
            
            // Get the list of all currently logged-in users
            var loggedInUsers = GetLoggedInUsers();

            foreach (var user in loggedInUsers)
            {
                userAccountLst.Items.Add(user);
            }
        }

        private string[] GetLoggedInUsers()
        {
            // Get the list of all currently running processes
            var processes = Process.GetProcesses();

            // Filter the list to unique user names
            var loggedInUsers = processes
                .Where(p => !string.IsNullOrEmpty(p.StartInfo.UserName))
                .Select(p => p.StartInfo.UserName)
                .Distinct()
                .ToArray();

            return loggedInUsers;
        }

        private void userAccountLst_SelectedIndexChanged(object sender, EventArgs e)
        {
            // Check if the selected user is still logged in
            var selectedUser = userAccountLst.SelectedItem.ToString();
            bool isLoggedIn = IsUserLoggedIn(selectedUser);

            if (isLoggedIn)
            {
                MessageBox.Show($"{selectedUser} is currently logged in.");
            }
            else
            {
                MessageBox.Show($"{selectedUser} is not logged in.");
            }
        }

        private bool IsUserLoggedIn(string username)
        {
            // Check if the specified username is in the list of logged-in users
            var loggedInUsers = GetLoggedInUsers();
            return loggedInUsers.Contains(username, StringComparer.OrdinalIgnoreCase);
        }
    }
}

try the below code and see if this works for you.

Dictionary userMap = new Dictionary();

private void popUserList()
{
    try
    {
        using (ManagementObjectSearcher usersSearcher = new ManagementObjectSearcher(@"SELECT * FROM Win32_UserAccount"))
        using (ManagementObjectCollection users = usersSearcher.Get())
        {
            var localUsers = users.Cast().Where(
                u => (bool)u["LocalAccount"] == true &&
                     int.Parse(u["SIDType"].ToString()) == 1 &&
                     u["Name"].ToString() != "HomeGroupUser$"
            );

            userMap.Clear();
            userAccountLst.Items.Clear();
            foreach (ManagementObject user in localUsers)
            {
                userMap[user["Name"].ToString()] = user;
                userAccountLst.Items.Add(user["Name"].ToString());
            }
        }
    }
    catch (Exception ex)
    {
        // Handle any exceptions that may occur during the WMI query.
        MessageBox.Show("Error while populating user list: " + ex.Message);
    }
}

private ManagementObject getCurrentUser()
{
    string selectedUser = userAccountLst.SelectedItem?.ToString();
    if (!string.IsNullOrEmpty(selectedUser) && userMap.ContainsKey(selectedUser))
    {
        return userMap[selectedUser];
    }
    return null;
}

private bool IsUserLoggedIn(ManagementObject user)
{
    if (user == null)
    {
        return false; // User not selected or not found in userMap.
    }

    try
    {
        using (ManagementObjectSearcher searcher = new ManagementObjectSearcher("SELECT * FROM Win32_UserProfile WHERE Loaded = True"))
        {
            foreach (ManagementObject obj in searcher.Get())
            {
                string antecedent = obj["Antecedent"].ToString();
                if (antecedent.Contains(user["Name"].ToString()))
                {
                    return true;
                }
            }
        }
    }
    catch (Exception ex)
    {
        // Handle any exceptions that may occur during the WMI query.
        MessageBox.Show("Error while checking user login status: " + ex.Message);
    }

    return false;
}

Please note that checking user login status based on Win32_UserProfile may not always provide reliable results due to differences in system behavior and configurations.