How to communicate with a windows service?

I could successfully handle the (almost) same issue as yours doing the following:

In your Class : ServiceBase, that represents your Service class, you might have:

public Class () //constructor, to create your log repository
    {
      InitializeComponent();

      if (!System.Diagnostics.EventLog.SourceExists("YOURSource"))
      {
        System.Diagnostics.EventLog.CreateEventSource(
           "YOURSource", "YOURLog");
      }
      eventLog1.Source = "YOURSource";
      eventLog1.Log = "YOURLog";
    }

Now, implement:

protected override void OnStart(string[] args)
{...}

AND

protected override void OnStop()
{...}

To handle custom commands calls:

protected override void OnCustomCommand(int command)
    {
      switch (command)
      {
        case 128:
          eventLog1.WriteEntry("Command " + command + " successfully called.");
          break;
        default:
          break;
      }
    }

Now, use this in the application where you'll call the Windows Service:

Enum to reference your methods: (remember, Services custom methods always receive an int32 (128 to 255) as parameters and using Enum you make it easier to remember and control your methods

private enum YourMethods
  {
    methodX = 128
  };

To call a specific method:

ServiceController sc = new ServiceController("YOURServiceName", Environment.MachineName);
ServiceControllerPermission scp = new ServiceControllerPermission(ServiceControllerPermissionAccess.Control, Environment.MachineName, "YOURServiceName");//this will grant permission to access the Service
    scp.Assert();
    sc.Refresh();

    sc.ExecuteCommand((int)YourMethods.methodX);

Doing this, you can control your service.

Here you can check how to create and install a Windows Service. More about the ExecuteCommand method.

Good luck!

If you are using .Net Framework 4, then memory mapped files provide a fairly easy way of implementing cross process communication.

It is fairly simple, and well described in documentation, and avoids the overhead (at runtime but also in terms of development effort) of using WCF or other connection/remoting based interactions, or of writing shared data to a central location and polling (database, file, etc).

See here for an overview.