How to initialize singleton class in Windows Service Hosted WCF Service on startup

Question

I wrote windows service hosted wcf service. Service behavior is: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)]

I read some data from DB and create some shared classes on startup. There are also some timers should work even if there is no request. Also initialization takes some time.

All this initialization happens in a singleton class which is in another dll. I try different signleton class initializations described here .

But the singleton class is not initialized until first request arrives. Timers, object loaded from DB ... etc. all of them is in this singleton class. After first request arrives everthing working just fine. Also service seems working on Services window even if classes are not initialized.

In debugger before a request arrives, dll doesn't even loading. How can i initilalize this singleton class on startup?

Is this a service behavior problem or should i change Windows Service installer?

EDIT: Reformat question.

Answer 1

You can start your WCF service on OnStart windows service event and stop it on OnStop windows event. You can add some diagnostic info to your windows event log to see if there is any exception and check if service is stared or not etc.

using System;
using System.ServiceModel;
using System.ServiceProcess;
using System.Diagnostics;
using System.Configuration;
using System.Timers;
using System.Collections.Generic;

namespace MyWCF
{
    public partial class WcfOverHttpService : ServiceBase
    {
        private ServiceHost m_host;

        public WcfOverHttpService()
        {
            System.Diagnostics.EventLog.WriteEntry(" WCF Interface", " Constructor called.", EventLogEntryType.Information);
            InitializeComponent();
        }

        protected override void OnStart(string[] args)
        {
            try
            {
                System.Diagnostics.EventLog.WriteEntry(" WCF Interface", "On Start called.", EventLogEntryType.Information);
                StartWcfService();
            }
            catch (Exception ex)
            {
                System.Diagnostics.EventLog.WriteEntry(" WCF Interface","On Start failed :"+ex.ToString(), EventLogEntryType.Error);
                throw ex;
            }
        }

         private void StartWcfService()
        {
            try
            {
                System.Diagnostics.EventLog.WriteEntry(" WCF Interface", "Start Wcf Service.", EventLogEntryType.Information);
                m_host = new ServiceHost(typeof(MyWCFService));
                m_host.Open();
                System.Diagnostics.EventLog.WriteEntry(" WCF Interface", "WCF Service HostOpen.", EventLogEntryType.Information);
            }
            catch (Exception ex)
            {
                System.Diagnostics.EventLog.WriteEntry(" WCF Interface", "Start WCF Service failed :" + ex.ToString(), EventLogEntryType.Error);
                throw ex;
            }
        }

        protected override void OnStop()
        {
            try
            {
                System.Diagnostics.EventLog.WriteEntry(" WCF Interface", "On Stop called.", EventLogEntryType.Information);
                if (m_host != null)
                {
                    System.Diagnostics.EventLog.WriteEntry(" WCF Interface", "Stop WCF Service.", EventLogEntryType.Information);
                    m_host.Close();
                    m_host = null;
                }

            }
            catch(Exception ex)
            {
                System.Diagnostics.EventLog.WriteEntry(" WCF Interface", "On Stop failed :" + ex.ToString(), EventLogEntryType.Error);
                throw ex;
                //handle exception
            }
        }

    }
}

This is how you could implement timer logic.

using System;
using System.ServiceModel;
using System.ServiceProcess;
using System.Diagnostics;
using System.Configuration;
using System.Timers;
using System.Collections.Generic;

namespace MyAppNameSpace
{
    public partial class MyWCFService : ServiceBase
    {
        private ServiceHost m_host;
        System.Timers.Timer MyProductionTimer = null;
        bool _MyProductionRunOnce = false;

        //// Put this values in Config 
        private string MyProductionSchedule = "DAILY";
        private string MyProductionToRun = "MANY";
        private string MyProductionStartTime = "10:00 PM";
        private int MyProductionPollInterval = 60000;


        public MyWCFService()
        {
            System.Diagnostics.EventLog.WriteEntry("My  WCF Interface Constructor", " Constructor called.", EventLogEntryType.Information);

            InitializeComponent();
            //Create Timer Object and register tick event
             this.MyProductionTimer = new System.Timers.Timer(MyProductionPollInterval);
             this.MyProductionTimer.Elapsed += new ElapsedEventHandler(this.MyProductionTimer_Tick);


        }

        protected override void OnStart(string[] args)
        {
            try
            {
                System.Diagnostics.EventLog.WriteEntry("My  WCF Interface Start", "On Start called.", EventLogEntryType.Information);

                StartWcfService();

                 // Setup timer and start it 
                this.MyProductionTimer.Interval = MyProductionPollInterval;
                this.MyProductionTimer.Enabled = true;
                this.MyProductionTimer.Start();
                System.Diagnostics.EventLog.WriteEntry("My  MyProduction Timer Start", "MyProduction Timer Start At :" + DateTime.Now.ToString(), EventLogEntryType.Information);

            }
            catch (Exception ex)
            {
                System.Diagnostics.EventLog.WriteEntry("My  WCF Interface Start Error","On Start failed :"+ex.ToString(), EventLogEntryType.Error);

                throw ex;
            }
        }

        protected override void OnStop()
        {
            try
            {
                System.Diagnostics.EventLog.WriteEntry("My  WCF Interface Stop", "On Stop called.", EventLogEntryType.Information);

                //Stop the timer
                this.MyProductionTimer.Stop();
                System.Diagnostics.EventLog.WriteEntry("My  MyProduction Timer Stop", "MyProduction Timer Stopped At :" + DateTime.Now.ToString(), EventLogEntryType.Information);

                if (m_host != null)
                {
                    System.Diagnostics.EventLog.WriteEntry("My  WCF Interface Stopped", "Stop Wc fService.", EventLogEntryType.Information);

                    m_host.Close();
                    m_host = null;
                }


            }
            catch(Exception ex)
            {
                System.Diagnostics.EventLog.WriteEntry("My  WCF Interface Stop Error", "On Stop failed :" + ex.ToString(), EventLogEntryType.Error);

                throw ex;
                //handle exception
            }
        }

        //Timer Tick Event
        private void MyProductionTimer_Tick(object sender, EventArgs e)
        {
            this.MyProductionTimer.Stop();
            this.MyProductionTimer.Interval = MyProductionPollInterval;
            bool runFlag = false;

            try
            {

                // Find out if it is time to run logic based on schedule
                string dw = DateTime.Now.DayOfWeek.ToString();

                if ((MyProductionSchedule.ToUpper() == "DAILY" && MyProductionToRun.ToUpper() == "ONCE") ||
                    (MyProductionSchedule.ToUpper() == dw.ToUpper() && MyProductionToRun.ToUpper() == "ONCE"))
                {
                    if (checkPolTime(MyProductionStartTime))
                        _MyProductionRunOnce = true;

                    if (_MyProductionRunOnce)
                    {
                        _MyProductionRunOnce = false;
                        runFlag = true;
                    }
                }
                else if ((MyProductionSchedule.ToUpper() == "DAILY" && MyProductionToRun.ToUpper() == "MANY") ||
                        (MyProductionSchedule.ToUpper() == dw.ToUpper() && MyProductionToRun.ToUpper() == "MANY"))
                {
                    if (!_MyProductionRunOnce)
                    {
                        if (checkPolTime(MyProductionStartTime))
                            _MyProductionRunOnce = true;
                    }

                    if (_MyProductionRunOnce)
                        runFlag = true;
                }
                else
                {
                    _MyProductionRunOnce = false;
                }

                if (runFlag)
                {
                    // Your Timer Business Logic  goes here
                }
            }
            catch (Exception exc)
            {
                System.Diagnostics.EventLog.WriteEntry(" MyProduction Timer Error",
                    exc.Message, EventLogEntryType.Error);
            }
            finally
            {
                this.MyProductionTimer.Start();//To restart the processing of production
            }
        }
        private void StartWcfService()
        {
            try
            {
                System.Diagnostics.EventLog.WriteEntry("My  WCF Interface Create Host", "Start Wcf Service.", EventLogEntryType.Information);
                m_host = new ServiceHost(typeof(WcfService));
                m_host.Open();
                System.Diagnostics.EventLog.WriteEntry("My  WCF Interface Host Opened", "WCF Service HostOpen.", EventLogEntryType.Information);
            }
            catch (Exception ex)
            {
                System.Diagnostics.EventLog.WriteEntry("My  WCF Interface Exception", "Start WCF Service failed :" + ex.ToString(), EventLogEntryType.Error);

                throw ex;
            }
        }

        // Utility to check if it is time to run the timer logic
        public static bool checkPolTime(string ProdStartTime)
        {
            DateTime t1 = DateTime.Now;
            DateTime t2 = Convert.ToDateTime(ProdStartTime);
            int i = DateTime.Compare(t1, t2);
            if (i >= 0)
            {
                return true;
            }
            else
            {
                return false;
           }
        }


    }
}