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

MessageProviderCollection

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); 

                } 

        } 

}

MessageProviderConfigurationSection

using System.Configuration; 

        /// Message的Provider的配置 

        public class MessageProviderConfigurationSection : ConfigurationSection 

                private readonly ConfigurationProperty _defaultProvider; 

                private readonly ConfigurationProperty _providers; 

                private ConfigurationPropertyCollection _properties; 

                /// 构造函数 

                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); 

                /// Message的默认的Provider 

                [ConfigurationProperty("defaultProvider")] 

                public string DefaultProvider 

                        get { return (string)base[_defaultProvider]; } 

                        set { base[_defaultProvider] = value; } 

                /// Message的所有的Provider集合 

                [ConfigurationProperty("providers", DefaultValue = "SqlMessageProvider")] 

                [StringValidator(MinLength = 1)] 

                public ProviderSettingsCollection Providers 

                        get { return (ProviderSettingsCollection)base[_providers]; } 

                /// Message的Provider的属性集合 

                protected override ConfigurationPropertyCollection Properties 

                        get { return _properties; } 

Message

using System.Collections.Generic; 

using System.Web.Configuration; 

        /// 暴露给客户端用的Message的类（Context） 

        public class Message 

                private static bool m_isInitialized = false; 

                private static MessageProviderCollection _providers = null; 

                private static MessageProvider _provider = null; 

                /// 静态构造函数，初始化 

                static Message() 

                        Initialize(); 

                /// 插入信息 

                /// <param name="mm">Message实体对象</param> 

                /// <returns></returns> 

                public static bool Insert(MessageModel mm) 

                        return _provider.Insert(mm); 

                /// 获取信息 

                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 

                                return _providers; 

Web.config

<?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>

Test

using System.Data; 

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()); 

运行结果

True

SQL方式，连接字符串是server=.;database=db;uid=sa;pwd=sa 2007-1-22 8:21:44

OK

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