Today I am going to show you how to host a WCF service in a managed environment such as windows service. Let us see how to achieve this through C#.
Here, I will first show you how to create a simple windows service and then how to host a WCF service in it.
I will also show you how to pass the external messages received on this service, to a host. I am going to use a singleton pattern to avoid the race condition while receiving messages concurrently.

1. Create a “Console Application” project named as “SelfHostService” using installed templates in Visual Studio
2. Delete Program.cs file from project
3. Add a new class named as SelfHostService.cs
4. Click Add Reference menu to open a Add Reference Dialog Box
5. Select System.ServiceProcess namespace to refer
6. ServiceBase class resides in this newly added namespace, which is required to create a service application. Derive SerivceBase class in SelfHostService class
7. Also add a reference to System.ServiceModel namespace
8. Now let us put some code in SelfHostService class

    public class SelfHostService : ServiceBase
    {
        public ServiceHost serviceHost = null;
        private bool startProcessing;        
        private static SelfHostService instance = null;
        private static readonly object padlock = new object();

        //a private constructor
        SelfHostService()
        {
            ServiceName = "Self Hosted Service";
        }

        //public static property to access the instance of the SelfHostService class
        public static SelfHostService Instance
        {
            get
            {
                lock (padlock)
                {
                    if (instance == null)
                        instance = new SelfHostService();

                    return instance;
                }
            }
        }
    }

9. In above code I have created a public property named Instance to provide a single instance of SelfHostService class
10. Now let us define a service contract IMessageListener

namespace SelfHostService
{
    public interface IMessageListener
    {
        bool AcceptMessages(string messsage);
    }
}

11. We will have to override OnStart() and OnStop() methods of ServiceBase class. These methods contains instructions to follow when service starts and stops respectively. Let us write a code for these methods

        protected override void OnStart(string[] args)
        {
             if (serviceHost != null)
                    serviceHost.Close();

                serviceHost = new ServiceHost(typeof(MessageListenerService));

                serviceHost.Open();

                var timer = new Timer();
                timer.Interval = 60000;
                timer.Elapsed += new ElapsedEventHandler(DoWork);
                timer.Start();
        }

        protected override void OnStop()
        {
            if (serviceHost != null)
            {
                serviceHost.Close();
                serviceHost = null;
            }
        }

12. DoWork method is a task assigned to a timer which has been initialized in OnStart() method. After every interval elapses, this method will get executed. So one can write any code which is to be performed repetitively by a window service.

        private void DoWork(object sender, ElapsedEventArgs e)
        {
            //Add code to do the intended work
        }

13. I will add a method to accept requests, received by MessageListenerService

        public bool AcceptExternalMessages(string message)
        {
            if (string.IsNullOrEmpty(message))
                return false;
            else
                return true;
        }

14. Now we will implement IMessageListener in MessageListenerService

    public class MessageListenerService : IMessageListener
    {
        public bool AcceptMessages(string message)
        {
            //Notify message to windows service
            return SelfHostService.Instance.AcceptExternalMessages(message);
        }
    }

15. We will have to configure the services’ base address, binding and contracts

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.serviceModel>    
	<services>
      <service name="SelfHostService.MessageListenerService" behaviorConfiguration="ServiceBehavior">
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:8082/SelfHostService/Service"/>
          </baseAddresses>
        </host>
        
        <endpoint address="" binding="wsHttpBinding" contract="SelfHostService.IMessageListener" />
        
        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="ServiceBehavior" >
          <serviceMetadata httpGetEnabled="true"/>
          <serviceDebug includeExceptionDetailInFaults="false"/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
</configuration>

In my next post I will write about how to install this service using InstallUtil.exe

Note: This code post is written in C# 6.0 in Visual Studio 2015