Hi mahesh213,

Refer below code.

Added references of System.DirectoryServices and System.Management.

Namespaces

using System.DirectoryServices;
using System.DirectoryServices.ActiveDirectory;
using System.Management;

Code

protected void Page_Load(object sender, EventArgs e)
{
    string corporate = "domain name";
    DirectoryEntry entry = new DirectoryEntry("LDAP://" + corporate);
    DirectoryContext objContext = new DirectoryContext(DirectoryContextType.Domain, corporate);
    Domain objDomain = Domain.GetDomain(objContext);
    string ldapPath = objDomain.Name;

    DirectorySearcher dSearch = new DirectorySearcher();
    dSearch.Filter = "(&(objectClass=computer)(objectCategory=computer))";
    dSearch.PropertiesToLoad.Add("cn");
    List<string> allComputers = new List<string>();
    foreach (SearchResult result in dSearch.FindAll())
    {
        string fqn = GetProperty(result, "cn") + "." + ldapPath;
        allComputers.Add(fqn);
    }

    foreach (object o in allComputers)
    {
        ConnectionOptions options = new ConnectionOptions();
        options.EnablePrivileges = true;
        options.Username = "username";
        options.Password = "pass@123";
        options.Impersonation = ImpersonationLevel.Impersonate;
        string fullComputerName = "\\\\" + o.ToString() + "\\root\\cimv2";
        ManagementScope scope = new ManagementScope(fullComputerName, options);
        try
        {
            scope.Connect();
        }
        catch (Exception ex)
        {
            string message = ex.Message;
            continue;
        }
        ObjectQuery query = new ObjectQuery("SELECT * FROM Win32_ComputerSystem");
        ManagementObjectSearcher searcher = new ManagementObjectSearcher(scope, query);
        ManagementObjectCollection queryCollection = searcher.Get();
        foreach (ManagementObject m in queryCollection)
        {
            Response.Write(string.Format("Logged On User : {0}", m["UserName"]));
        }
    }
}

private static string GetProperty(SearchResult sr, string propertyName)
{
    if (sr.Properties.Contains(propertyName))
    {
        return sr.Properties[propertyName][0].ToString();
    }

    return string.Empty;
}

Reference:

https://social.msdn.microsoft.com/Forums/en-US/5e6ef3c3-ee9c-4d45-9f14-8722b084b710/how-to-check-if-a-user-is-logged-on?forum=csharplanguage