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

using System.Configuration.Provider; 
using System; 
 
namespace Pattern.Provider 
{ 
         /// <summary> 
         /// Message的Provider集合类 
         /// </summary> 
         public  class MessageProviderCollection : ProviderCollection 
        { 
                 /// <summary> 
                 /// 向集合中添加提供程序。 
                 /// </summary> 
                 /// <param name="provider">要添加的提供程序。</param> 
                 public  override  void Add(ProviderBase provider) 
                { 
                         if (provider ==  null) 
                                 throw  new ArgumentNullException( "provider参数不能为null"); 
 
                         if (!(provider  is MessageProvider)) 
                                 throw  new ArgumentException( "provider参数类型必须是MessageProvider."); 
 
                         base.Add(provider); 
                } 
        } 
}

using System.Configuration; 
 
namespace Pattern.Provider 
{ 
         /// <summary> 
         /// Message的Provider的配置 
         /// </summary> 
         public  class MessageProviderConfigurationSection : ConfigurationSection 
        { 
                 private  readonly ConfigurationProperty _defaultProvider; 
                 private  readonly ConfigurationProperty _providers; 
                 private ConfigurationPropertyCollection _properties; 
                 
                 /// <summary> 
                 /// 构造函数 
                 /// </summary> 
                 public MessageProviderConfigurationSection() 
                { 
                        _defaultProvider =  new ConfigurationProperty( "defaultProvider",  typeof( string),  null); 
                        _providers =  new ConfigurationProperty( "providers",  typeof(ProviderSettingsCollection),  null); 
                        _properties =  new ConfigurationPropertyCollection(); 
 
                        _properties.Add(_providers); 
                        _properties.Add(_defaultProvider); 
                } 
 
                 /// <summary> 
                 /// Message的默认的Provider 
                 /// </summary> 
                [ConfigurationProperty( "defaultProvider")] 
                 public  string DefaultProvider 
                { 
                        get {  return ( string) base[_defaultProvider]; } 
                        set {  base[_defaultProvider] = value; } 
                } 
 
                 /// <summary> 
                 /// Message的所有的Provider集合 
                 /// </summary> 
                [ConfigurationProperty( "providers", DefaultValue =  "SqlMessageProvider")] 
                [StringValidator(MinLength = 1)] 
                 public ProviderSettingsCollection Providers 
                { 
                        get {  return (ProviderSettingsCollection) base[_providers]; } 
                } 
 
                 /// <summary> 
                 /// Message的Provider的属性集合 
                 /// </summary> 
                 protected  override ConfigurationPropertyCollection Properties 
                { 
                        get {  return _properties; } 
                } 
        } 
}

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; 
                        } 
                } 
        } 
}

<?xml version="1.0" encoding="utf-8"?> 
<configuration> 
    <configSections> 
        <section name="MessageProvider" type="Pattern.Provider.MessageProviderConfigurationSection, Pattern.Provider" /> 
    </configSections> 
    <MessageProvider defaultProvider="SqlMessageProvider"> 
        <providers> 
            <add name="XmlMessageProvider" type="Pattern.Provider.XmlMessageProvider, Pattern.Provider" connectionStringName="XmlConnection" /> 
            <add name="SqlMessageProvider" type="Pattern.Provider.SqlMessageProvider, Pattern.Provider" connectionStringName="SqlConnection" /> 
        </providers> 
    </MessageProvider> 
    <connectionStrings> 
        <add name="SqlConnection" connectionString="server=.;database=db;uid=sa;pwd=sa" /> 
        <add name="XmlConnection" connectionString="XmlPath" /> 
    </connectionStrings> 
</configuration>

using System; 
using System.Data; 
using System.Configuration; 
using System.Collections; 
using System.Web; 
using System.Web.Security; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Web.UI.WebControls.WebParts; 
using System.Web.UI.HtmlControls; 
 
using Pattern.Provider; 
 
public partial  class Provider : System.Web.UI.Page 
{ 
         protected  void Page_Load( object sender, EventArgs e) 
        { 
                Response.Write(Message.Insert( new MessageModel( "插入", DateTime.Now))); 
                Response.Write( "<br />"); 
                Response.Write(Message.Get()[0].Message +  " " + Message.Get()[0].PublishTime.ToString()); 
        } 
}

     本文转自webabcd 51CTO博客，原文链接：http://blog.51cto.com/webabcd/344595，如需转载请自行联系原作者