How to communicate to Windows Service through WCF?

Question

I have Windows Service, which is running tasks on timer tick. I also selected to communicate with Windows Service through WCF named pipe channel. I can create WCF Service instance and open it for listening. But how I access objects relying in Windows Service via WCF?

This is what my Windows Service looks like:

public partial class MyService : ServiceBase
{
    private ServiceHost m_svcHost = null;  
    private myObject = null;

    ...

    // Run this method from external WCF client
    private void SomeMethod()
    {
    }

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

        m_svcHost = new ServiceHost(typeof(MyCommunicationService));
        m_svcHost.Open();

        // initialize and work with myObject
    }

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

So what I want, to have access to myObject within WCF Service, when client will make inquiry. Or even run a method on myObject.

Answer 1

You can create a communication channel between your MyService (WCF Hosting entity) and the MyCommunicationService (WCF Service instance) simply using a static property:

//This can be put into a separate DLL if needed.
public interface IMyHostCallbacks
{
    void HostCallback(string iSomeDataFromWCFToHost);
}

public static class Host
{
    public static IMyHostCallbacks Current;
}

---

public partial class MyService : ServiceBase, IMyHostCallbacks
{
    protected override void OnStart(string[] args)
    {
        //Set the static callback reference.
        Host.Current = this;

        if (m_svcHost != null) m_svcHost.Close();

        m_svcHost = new ServiceHost(typeof(MyCommunicationService));
        m_svcHost.Open();

        // initialize and work with myObject
    }

    //Here you have data from WCF and myObject available.
    void IMyHostCallbacks.HostCallback(string iSomeDataFromWCFToHost)
    {
        //Be careful here. 
        //Depending on your WCF service and WCF clients this might 
        //get called simultaneously from different threads.
        lock(myObject)
        {
            myObject.DoSomething(iSomeDataFromWCFToHost);
        }
    }
}

Surely you can even put the static field into your MyService class but at least some abstraction between MyService and MyCommunicationService would not hurt.

---

Now, in any place in your MyCommunicationService you can:

void WCFServiceMethod()
{
    Host.Current.HostCallback("some data");
}