This is derived from actual code of mine, and elements of this sample combine the Facade pattern with the Publisher (Observer) pattern.  The primary class, based on the ISubscriber interface, is fairly complicated to use, requiring delegates, threading, and asynchronous callbacks.  The facade, based on ISubscriberFacade, encapsulates all the methods required to work with the Windows Communication Foundation (WCF) service , handling threading, delegate creation, and asynchronous callbacks internally, so that that the clients only need to create the object.  I wrote the encapsulating client to ease the adoption of the WCF service for legacy clients, seeing that the code complexity was likely a hurdle.

Salient Characteristic(s)

  • Reduces or hides complexities to other clients or systems
  • Simplified interaction between systems and/or types

  • DispatchingObservableCollection is based on ObservableCollection commonly used in Windows Presentation Foundation (WPF) applications and available from one of my other sites.
  • Some classes are not available in this example, i.e., TrackedConnections, CubeInfo, and ConfigurationList, since they are part of the larger project, and would detract his example

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Net;
using System.Reflection;
using System.ServiceModel;
using System.Threading;

namespace DesignPatterns
    public interface ISubscriber
        string UserId { get; set; }
        string Workstation { get; set; }
        string Title { get; set; }
        string Host { get; set; }
        string Port { get; set; }

        bool IsConnected { get; }
        TrackedConnections Tracker { get; set; }

        [OperationContract(IsOneWay = false)]
        void Attach(string userId, string workstation, string application);

        # region Methods used for Excel clients, used with delegate for status updates

        [OperationContract(IsOneWay = true)]
        void Update(IList<CubeInfo> message);

        [OperationContract(IsOneWay = false)]
        void Run();

        [OperationContract(IsOneWay = false)]
        void SendWorkbokForTracking(TrackedConnection item);

        UserConfigurationList Configuration { get; set; }

        # endregion

        # region Methods for legacy clients - single execution with return

        [OperationContract(IsOneWay = false)]
        IList<CubeInfo> GetAvailableCubeStatus();

        [OperationContract(IsOneWay = false)]
        CubeInfo GetActiveCube();

        # endregion

        # region Load Status methods - returns slices to load information

        [OperationContract(IsOneWay = false)]
        DataSet GetLoadStatusByDate(string viewDate);

        [OperationContract(IsOneWay = false)]
        DataSet GetLoadStatusBySource(string viewDate);

        [OperationContract(IsOneWay = false)]
        DataSet GetLoadStatusByRegion(string viewDate);

        # endregion

    interface ISubscriberFacade
        event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

        DispatchingObservableCollection<CubeInfo> ActiveCubes { get; }
        DispatchingObservableCollection<CubeInfo> CubeList { get; }
        CubeInfo ActiveCube { get; }

        void Connect();
        void Detach();
        void Dispose();

        string Host { get; }
        string Port { get; }

        bool Status { get; }
        DateTime TimeStamp { get; }
        string AsString { get; }
        string ToString();
        bool UseWindowsAuthentication { get; }

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