two guys from kc

Determining if someone is logged into a remote computer, either interactively or remotely, is not as easy as it sounds. A quick solution however is to merely enumerate the explorer.exe process (which will not be running if nobody is logged in):

 public static bool isAnyoneLoggedOn(string computer_name)
 {
     Console.Write("Looking for users on " + computer_name + "... ");
     try
     {
         ConnectionOptions oConn = new ConnectionOptions();
         System.Management.ManagementScope oMs = new System.Management.ManagementScope("\\\\" + computer_name + "\\root\\cimv2", oConn);

         //get explorer.exe process instances
         System.Management.ObjectQuery oQuery = new System.Management.ObjectQuery("Select * from Win32_Process Where Name = 'explorer.exe'");

         //Execute the query
         ManagementObjectSearcher oSearcher = new ManagementObjectSearcher(oMs, oQuery);

         //Get the results
         ManagementObjectCollection oReturnCollection = oSearcher.Get();
         if (oReturnCollection.Count == 0)
         {
             Console.WriteLine("No Users.");
             return false;
         }
         else
         {
             Console.WriteLine("Found User.");
             return true;
         }
     }
     catch (Exception M)
     {
         // Probably an access denied error. In my case I must assume someone is logged in.
         string errorMessage = "Error in isAnyoneLoggedOn() on " + computer_name + ": " + M.Message;
         Console.WriteLine(errorMessage);
         return true;
     }
 }