How to kill a thread in C# effectively?

Question

I am not trying to beat a dead horse, honestly. And I've read all the advice on thread killing, however, please consider the code. It does the following:

1. It starts a thread (via StartThread method)
2. It calls the database looking for anything in the ServiceBroker queue. Note the WAITFOR command - it means that it will sit there until there is something in the queue. All this in MonitorQueue method.

3. Kill the thread. I tried .Interrupt - it seems to do absolutely nothing. Then I tried .Abort, which should never be used, but even that did nothing.

   Thread thxMonitor = new Thread(MonitorQueue);
   void StartThread() {
       thxMonitor.Start();
   }
   
   void MonitorQueue(object obj) {
       var conn = new SqlConnection(connString);
       conn.Open();
       var cmd = conn.CreateCommand();
       cmd.CommandTimeout = 0; // forever and ever
       cmd.CommandType = CommandType.Text;
       cmd.CommandText = "WAITFOR (RECEIVE CONVERT(int, message_body) AS Message FROM SBQ)";
   
       var dataTable = new DataTable();
       var da = new SqlDataAdapter(command);
   
       da.Fill(dataTable);
       da.Dispose();
   }
   
   void KillThreadByAnyMeansNecessary() {
       thxMonitor.Interrupt();
       thxMonitor.Abort();
   }
   

Is it actually possible to kill a thread?

Answer 1

Set an Abort flag to tell the thread is needs to terminate. Append a dummy record to the ServiceBroker queue. The WAITFOR then returns. The thread then checks its 'Abort' flag and, finding it set, deletes the dummy record from the queue and exits.

Another variant would be to add a 'real' poison-pill record to the specification for the table monitored by the ServiceBroker - an illegal record-number, or the like. That would avoid touching the thread/s at all in any direct manner - always a good thing:) This might be more complex, especially if each work thread is expeceted to notify upon actual termination, but would still be effective if the work threads, ServiceBroker and DB were all on different boxes. I added this as an edit because, having thought a bit more about it, it seems more flexible, after all, if the threads normally only communicate via. the DB, why not shut them down with only the DB? No Abort(), no Interrupt() and, hopefully, no lockup-generating Join().