HandlerChain_Class.cs

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using System;
using System.Collections.Generic;
using System.Text;
 
namespace DesignPatternExamples_csharp
{
    public interface IMessageHandler
    {
        int ID { get; }
 
        bool ProcessMessage(Message message);
 
        string ToString();
    }
 
 
 
    //========================================================================
    //========================================================================
    //========================================================================
 
 
 
    public class HandlerChain
    {
        List<IMessageHandler> _messageHandlers = new List<IMessageHandler>();
 
        object _messageHandlersLock = new object();
 
 
        public void SendMessage(Message message)
        {
            // We make a copy of the handlers so our processing of handlers
            // is not impacted by updates to the master handler list.
            IMessageHandler[] copyof_MessageHandlers;
            lock (_messageHandlersLock)
            {
                copyof_MessageHandlers = new IMessageHandler[_messageHandlers.Count];
                _messageHandlers.CopyTo(copyof_MessageHandlers);
            }
 
            foreach (IMessageHandler window in copyof_MessageHandlers)
            {
                if (window.ProcessMessage(message))
                {
                    break;
                }
            }
        }
 
 
        public void AddHandler(IMessageHandler window)
        {
            lock (_messageHandlersLock)
            {
                // Add the handler if not already in the list.
                if (_messageHandlers.FindIndex(w => w.ID == window.ID) == -1)
                {
                    _messageHandlers.Add(window);
                }
            }
        }
 
 
        public void RemoveHandler(IMessageHandler window)
        {
            lock(_messageHandlersLock)
            {
                int foundIndex = _messageHandlers.FindIndex(w => w.ID == window.ID);
                if (foundIndex != -1)
                {
                    _messageHandlers.RemoveAt(foundIndex);
                }
            }
        }
 
 
        public override string ToString()
        {
            StringBuilder output = new StringBuilder();
 
            IMessageHandler[] copyof_MessageHandlers;
            lock (_messageHandlersLock)
            {
                copyof_MessageHandlers = new IMessageHandler[_messageHandlers.Count];
                _messageHandlers.CopyTo(copyof_MessageHandlers);
            }
 
            foreach (IMessageHandler window in copyof_MessageHandlers)
            {
                output.AppendFormat("    {0}{1}", window.ToString(), Environment.NewLine);
            }
            return output.ToString();
        }
    }
}