Hi , I am using the console application i used multi threading in the same. I just want to know which section have to put inside critical section my code is : .------------------------------------------------------------------------------.
public class SendBusReachSMS {

    public void SchedularEntryPoint()
    {
        try
        {
            List<ActiveBusAndItsPathInfo> ActiveBusAndItsPathInfoList = BusinessLayer.GetActiveBusAndItsPathInfoList();
            if (ActiveBusAndItsPathInfoList != null)
            {
                //SMSThreadEntryPoint smsentrypoint = new SMSThreadEntryPoint();
                while (true)
                {
                    foreach (ActiveBusAndItsPathInfo ActiveBusAndItsPathInfoObj in ActiveBusAndItsPathInfoList)
                    {
                        if (ActiveBusAndItsPathInfoObj.isSMSThreadActive == false)
                        {

                            DateTime CurrentTime = System.DateTime.Now;
                            DateTime Bustime = Convert.ToDateTime(ActiveBusAndItsPathInfoObj.busObj.Timing);
                            TimeSpan tsa = Bustime - CurrentTime;

                            if (tsa.TotalMinutes > 0 && tsa.TotalMinutes < 5)
                            {
                                ThreadStart starter = delegate { SMSThreadEntryPointFunction(ActiveBusAndItsPathInfoObj); };
                                Thread t = new Thread(starter);
                                t.Start();
                                 t.Join();
                            }
                        }
                    }
                }
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("===========================================");
            Console.WriteLine(ex.Message);
            Console.WriteLine(ex.InnerException);
            Console.WriteLine("===========================================");
        }
    }


    public void SMSThreadEntryPointFunction(ActiveBusAndItsPathInfo objActiveBusAndItsPathInfo)
    {
        try
        {
            //mutThrd.WaitOne();
            String consoleString = "Thread for " + objActiveBusAndItsPathInfo.busObj.Number + "\t" + " on path " + "\t" + objActiveBusAndItsPathInfo.pathObj.PathId;
            Console.WriteLine(consoleString);
            TrackingInfo trackingObj = new TrackingInfo();
            string strTempBusTime = objActiveBusAndItsPathInfo.busObj.Timing;
            while (true)
            {

                trackingObj = BusinessLayer.get_TrackingInfoForSendingSMS(objActiveBusAndItsPathInfo.busObj.Number);

                if (trackingObj.latitude != 0.0 && trackingObj.longitude != 0.0)
                {
                    //calculate distance
                    double distanceOfCurrentToDestination = 4.45;
                    TimeSpan CurrentTime = System.DateTime.Now.TimeOfDay;
                    TimeSpan timeLimit = objActiveBusAndItsPathInfo.sessionInTime - CurrentTime;
                    if ((distanceOfCurrentToDestination <= 5) && (timeLimit.TotalMinutes <= 5))
                    {
                        Console.WriteLine("Message sent to bus number's parents: " + objActiveBusAndItsPathInfo.busObj.Number);
                        break;
                    }
                }
            }
           // mutThrd.ReleaseMutex();
        }
        catch (Exception ex)
        {
            //throw;
            Console.WriteLine("===========================================");
            Console.WriteLine(ex.Message);
            Console.WriteLine(ex.InnerException);
            Console.WriteLine("===========================================");
        }

    }

}

Please help me in multithreading. new topic for me in .net