public class NewIssueAvailableEventArgs : EventArgs

{

    public string hyperlinkURL;

    public string issueNumber;

    public DateTime datePublished;

}

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]

public class MagazineService : IMagazineService

{

    public static event NewIssueAvailableHandler NewIssueAvailableEvent;

    public delegate void NewIssueAvailableHandler(object sender, NewIssueAvailableEventArgs e);

    // instance of eventhandler

    NewIssueAvailableHandler newIssueHandler;

    // Callback to individual clients using the ClientContract

    IClientContract callback = null;

    public void PublishMagazine(string hyperLinkToIssue, string issueNumber, DateTime datePublished)

    {

        NewIssueAvailableEventArgs eargs = new NewIssueAvailableEventArgs();

        eargs.hyperlinkURL = hyperLinkToIssue;

        eargs.issueNumber = issueNumber;

        eargs.datePublished = datePublished;

        // fire the event

        NewIssueAvailableEvent(this, eargs);

    }

    public void Subscribe()

    {

        callback = OperationContext.Current.GetCallbackChannel<IClientContract>();

        // this is the handler that we will 'unsubscribe' from later

        newIssueHandler = new NewIssueAvailableHandler(MagazineService_NewIssueAvailableEvent);

        NewIssueAvailableEvent += newIssueHandler;

    }

    public void Unsubscribe()

    {

        NewIssueAvailableEvent -= newIssueHandler;

    }

    public void MagazineService_NewIssueAvailableEvent(object sender, NewIssueAvailableEventArgs e)

    {

        callback.MessageReceived(e.hyperlinkURL, e.issueNumber, e.datePublished);

    }

}