上接乐在其中设计模式(C#) - 提供者模式(Provider Pattern)

using System; 
using System.Collections.Generic; 
using System.Configuration; 
using System.Web.Configuration; 
 
namespace Pattern.Provider 
{ 
         /// <summary> 
         /// 暴露给客户端用的Message的类（Context） 
         /// </summary> 
         public  class Message 
        { 
                 private  static  bool m_isInitialized =  false; 
                 private  static MessageProviderCollection _providers =  null; 
                 private  static MessageProvider _provider =  null; 
 
                 /// <summary> 
                 /// 静态构造函数，初始化 
                 /// </summary> 
                 static Message() 
                { 
                        Initialize(); 
                } 
 
                 /// <summary> 
                 /// 插入信息 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 /// <returns></returns> 
                 public  static  bool Insert(MessageModel mm) 
                { 
                         return _provider.Insert(mm); 
                } 
 
                 /// <summary> 
                 /// 获取信息 
                 /// </summary> 
                 /// <returns></returns> 
                 public  static List<MessageModel> Get() 
                { 
                         return _provider.Get(); 
                } 
 
                 private  static  void Initialize() 
                { 
                         try 
                        { 
                                MessageProviderConfigurationSection messageConfig =  null; 
 
                                 if (!m_isInitialized) 
                                { 
 
                                         // 找到配置文件中“MessageProvider”节点 
                                        messageConfig = (MessageProviderConfigurationSection)ConfigurationManager.GetSection( "MessageProvider"); 
 
                                         if (messageConfig ==  null) 
                                                 throw  new ConfigurationErrorsException( "在配置文件中没找到“MessageProvider”节点"); 
 
                                        _providers =  new MessageProviderCollection(); 
 
                                         // 使用System.Web.Configuration.ProvidersHelper类调用每个Provider的Initialize()方法 
                                        ProvidersHelper.InstantiateProviders(messageConfig.Providers, _providers,  typeof(MessageProvider)); 
 
                                         // 所用的Provider为配置中默认的Provider 
                                        _provider = _providers[messageConfig.DefaultProvider]  as MessageProvider; 
 
                                        m_isInitialized =  true; 
 
                                } 
                        } 
                         catch (Exception ex) 
                        { 
                                 string msg = ex.Message; 
                                 throw  new Exception(msg); 
                        } 
                } 
 
                 private  static MessageProvider Provider 
                { 
                        get 
                        { 
                                 return _provider; 
                        } 
                } 
 
                 private  static MessageProviderCollection Providers 
                { 
                        get 
                        { 
                                 return _providers; 
                        } 
                } 
        } 
}