大哥们帮忙看看这段没错的代码

Question

using System;
using System.Reflection;
using System.Collections.Specialized;
using System.Configuration.Provider;
using System.Data;
using System.Web.Caching;
using System.Web;
using System.Web.Configuration;
using System.Configuration;
namespace Commerce.Providers {    public abstract class CatalogProvider : System.Configuration.Provider.ProviderBase
    {        static CatalogProvider _instance;        static object padLock;
        public static CatalogProvider Instance {            get {
                CatalogProvider tempInstance;
                if (_instance == null)
                    padLock = new object();
                lock (padLock) {
                    tempInstance = LoadProvider();
                    _instance = tempInstance;
                }                return _instance;
            }
        }
        static CatalogProvider LoadProvider() {            // Get the names of the providers
            // Use the cache because the reflection used later is expensive
            Cache cache = System.Web.HttpRuntime.Cache;
            string cacheKey = null;            CatalogProvider _instanceLoader;
            CatalogProviderConfiguration config = CatalogProviderConfiguration.GetConfig();
            cacheKey = "CatalogProvider::" + config.DefaultProvider;
            object oProvider = cache.Get(cacheKey);
            if (oProvider != null) {
                _instanceLoader = (CatalogProvider)oProvider;
            } else {                try {                    // Read the configuration specific information for this provider
                    Provider CatalogProvider = (Provider)config.Providers[config.DefaultProvider];                    // The assembly should be in \bin or GAC
                    Type type = Type.GetType(CatalogProvider.Type);
                    _instanceLoader = (CatalogProvider)Activator.CreateInstance(type);                    // Initialize the provider with the attributes.
                    string cStringName = CatalogProvider.Attributes["connectionStringName"];
                    string cString = System.Configuration.ConfigurationManager.ConnectionStrings[cStringName].ConnectionString;
                    CatalogProvider.Attributes.Add("connectionString", cString);
                    _instanceLoader.Initialize(CatalogProvider.Name, CatalogProvider.Attributes);                    //pop it into the cache to keep out site from running into the ground :)
                    cache.Insert(cacheKey, _instanceLoader);                } catch (Exception e) {
                    throw new Exception("Unable to load provider", e);
                }
            }
            return _instanceLoader;
        }
///LoadProvider和Instance 各实现什么的功能？
这里为什么能使用CatalogProvider ？

Answer 1

public static CatalogProvider Instance {
的操作就是得到一个CatalogProvider 的对象LoadProvider()是这个对象的 现实原理
这里应该是 用于CatalogProvider 对象的cache缓存的一个实现

Answer 2

在类CatalogProvider 引用CatalogProvider 
这是一个怎样的想法？

Answer 3

是不是Instance的方法之后可以这样字引用
Commerce.Providers.CatalogProvider.Instance.方法

Answer 4

public abstract class CatalogProvider : System.Configuration.Provider.ProviderBase
    {        static CatalogProvider _instance; //单件模式        static object padLock;           //同步锁
        public static CatalogProvider Instance {  //单件模式            get {
                CatalogProvider tempInstance;
                if (_instance == null)
                    padLock = new object();
                lock (padLock) {
                    tempInstance = LoadProvider();
                    _instance = tempInstance;
                }                return _instance;
            }
        }
        static CatalogProvider LoadProvider() {            // Get the names of the providers
            // Use the cache because the reflection used later is expensive
            Cache cache = System.Web.HttpRuntime.Cache;
            string cacheKey = null;            CatalogProvider _instanceLoader;
            CatalogProviderConfiguration config = CatalogProviderConfiguration.GetConfig();
            cacheKey = "CatalogProvider::" + config.DefaultProvider;
            object oProvider = cache.Get(cacheKey); //试图从缓存中获取对象
            if (oProvider != null) {
                _instanceLoader = (CatalogProvider)oProvider;
            } else {
                   //如果缓存中没有，就实例化一个
                try {                    // Read the configuration specific information for this provider
                    Provider CatalogProvider = (Provider)config.Providers[config.DefaultProvider];                    // The assembly should be in \bin or GAC
                    Type type = Type.GetType(CatalogProvider.Type);
                    _instanceLoader = (CatalogProvider)Activator.CreateInstance(type);                    // Initialize the provider with the attributes.
                    string cStringName = CatalogProvider.Attributes["connectionStringName"];
                    string cString = System.Configuration.ConfigurationManager.ConnectionStrings[cStringName].ConnectionString;
                    CatalogProvider.Attributes.Add("connectionString", cString);
                    _instanceLoader.Initialize(CatalogProvider.Name, CatalogProvider.Attributes);                    //pop it into the cache to keep out site from running into the ground :)
                    cache.Insert(cacheKey, _instanceLoader);                } catch (Exception e) {
                    throw new Exception("Unable to load provider", e);
                }
            }
            return _instanceLoader;
        }