C# IoC学习笔记

    一、引言

    面向接口(抽象)编程，是为了降低程序的耦合度，符合依赖倒置原则。因此典型的三层架构ui、bll、dal基于接口设计后，会拓展成ui、ibll、bll、idal、dal。在上一篇《c# ioc学习笔记》中我们可以了解到，控制反转(ioc)使对象的创建交给了第三方ioc容器如unity。利用unity的ioc功能，可以对基于接口设计的三层架构做进一步的升级，搭建一个更容易实现的可配置可扩展的三层架构；利用unity的aop功能，使框架更加的简洁，因为它抽出了框架的公共逻辑部分。

    二、项目建立

    2.1、项目建立

    依次新建项目ui(client)、ibll、bll、idal、dal、model、common。

    2.2项目说明

    三、项目之间的引用关系

    3.1、对着项目名称右键->添加->引用->项目，添加各个项目的引用。

    3.2、引用说明

    四、项目需安装的nuget包

 

     五、注意事项

    对unity容器的ioc调用进行封装，container应封装成单例模式以提高效率，此处使用memorycache。

    5.1、在common项目引用system.runtime.caching.dll，并在helper文件夹下新建一个缓存帮助类：memorycachehelper.cs。

    /// <summary>
    /// 内存缓存帮助类，支持绝对过期时间、滑动过期时间、文件依赖三种缓存方式。
    /// </summary>
    class memorycachehelper
    {
        private static readonly object _locker1 = new object(), _locker2 = new object();

        /// <summary>
        /// 取缓存项，如果不存在则返回空。
        /// </summary>
        /// <typeparam name="t"></typeparam>
        /// <param name="key"></param>
        /// <returns></returns>
        public static t getcacheitem<t>(string key)
        {
            try
            {
                return (t)memorycache.default[key];
            }
            catch
            {
                return default(t);
            }
        }

        /// <summary>
        /// 是否包含指定键的缓存项
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static bool contains(string key)
        {
            return memorycache.default.contains(key);
        }

        /// <summary>
        /// 取缓存项，如果不存在则新增缓存项。
        /// </summary>
        /// <typeparam name="t"></typeparam>
        /// <param name="key"></param>
        /// <param name="cachepopulate"></param>
        /// <param name="slidingexpiration"></param>
        /// <param name="absoluteexpiration"></param>
        /// <returns></returns>
        public static t getoraddcacheitem<t>(string key, func<t> cachepopulate, timespan? slidingexpiration = null, datetime? absoluteexpiration = null)
        {
            if (string.isnullorwhitespace(key)) throw new argumentexception("invalid cache key");
            if (cachepopulate == null) throw new argumentnullexception("cachepopulate");
            if (slidingexpiration == null && absoluteexpiration == null) throw new argumentexception("either a sliding expiration or absolute must be provided");

            if (memorycache.default[key] == null)
            {
                lock (_locker1)
                {
                    if (memorycache.default[key] == null)
                    {
                        t cachevalue = cachepopulate();
                        if (!typeof(t).isvaluetype && cachevalue == null)   //如果是引用类型且为null则不存缓存
                        {
                            return cachevalue;
                        }

                        var item = new cacheitem(key, cachevalue);
                        var policy = createpolicy(slidingexpiration, absoluteexpiration);

                        memorycache.default.add(item, policy);
                    }
                }
            }

            return (t)memorycache.default[key];
        }

        /// <summary>
        /// 取缓存项，如果不存在则新增缓存项。
        /// </summary>
        /// <typeparam name="t"></typeparam>
        /// <param name="key"></param>
        /// <param name="cachepopulate"></param>
        /// <param name="dependencyfilepath"></param>
        /// <returns></returns>
        public static t getoraddcacheitem<t>(string key, func<t> cachepopulate, string dependencyfilepath)
        {
            if (string.isnullorwhitespace(key)) throw new argumentexception("invalid cache key");
            if (cachepopulate == null) throw new argumentnullexception("cachepopulate");

            if (memorycache.default[key] == null)
            {
                lock (_locker2)
                {
                    if (memorycache.default[key] == null)
                    {
                        t cachevalue = cachepopulate();
                        if (!typeof(t).isvaluetype && cachevalue == null)   //如果是引用类型且为null则不存缓存
                        {
                            return cachevalue;
                        }

                        var item = new cacheitem(key, cachevalue);
                        var policy = createpolicy(dependencyfilepath);

                        memorycache.default.add(item, policy);
                    }
                }
            }

            return (t)memorycache.default[key];
        }

        /// <summary>
        /// 指定缓存项的一组逐出和过期详细信息
        /// </summary>
        /// <param name="slidingexpiration"></param>
        /// <param name="absoluteexpiration"></param>
        /// <returns></returns>
        private static cacheitempolicy createpolicy(timespan? slidingexpiration, datetime? absoluteexpiration)
        {
            var policy = new cacheitempolicy();

            if (absoluteexpiration.hasvalue)
            {
                policy.absoluteexpiration = absoluteexpiration.value;
            }
            else if (slidingexpiration.hasvalue)
            {
                policy.slidingexpiration = slidingexpiration.value;
            }

            policy.priority = cacheitempriority.default;

            return policy;
        }

        /// <summary>
        /// 指定缓存项的一组逐出和过期详细信息
        /// </summary>
        /// <param name="filepath"></param>
        /// <returns></returns>
        private static cacheitempolicy createpolicy(string filepath)
        {
            cacheitempolicy policy = new cacheitempolicy();
            policy.changemonitors.add(new hostfilechangemonitor(new list<string>() { filepath }));
            policy.priority = cacheitempriority.default;
            return policy;
        }

        /// <summary>
        /// 移除指定键的缓存项
        /// </summary>
        /// <param name="key"></param>
        public static void removecacheitem(string key)
        {
            if (contains(key))
            {
                memorycache.default.remove(key);
            }
        }
    }

    5.2、在common项目helper文件夹下面新建一个unity帮助类：unityhelper.cs，并实现container的缓存。

    /// <summary>
    /// unity容器帮助类
    /// </summary>
    public static class unityhelper
    {
        /// <summary>
        /// unity容器创建对象(不含别名)
        /// </summary>
        /// <param name="containername">容器名称</param>
        /// <returns></returns>
        public static t getobject<t>(string containername)
        {
            iunitycontainer container = memorycachehelper.getoraddcacheitem(containername, () =>
            {
                iunitycontainer unitycontainer = new unitycontainer();
                execonfigurationfilemap filemap = new execonfigurationfilemap
                {
                    execonfigfilename = path.combine(appdomain.currentdomain.basedirectory + @"configfiles\unity.config")
                };
                configuration configuration = configurationmanager.openmappedexeconfiguration(filemap, configurationuserlevel.none);
                unityconfigurationsection configsection = (unityconfigurationsection)configuration.getsection(unityconfigurationsection.sectionname);
                configsection.configure(unitycontainer, containername);
                return unitycontainer;
            },timespan.fromminutes(30),null);
            
            return container.resolve<t>();
        }

        /// <summary>
        /// unity容器创建对象(含别名)
        /// </summary>
        /// <typeparam name="t"></typeparam>
        /// <param name="containername">容器名称</param>
        /// <param name="alisname">对象别名</param>
        /// <returns></returns>
        public static t getobject<t>(string containername, string alisname)
        {
            iunitycontainer container = memorycachehelper.getoraddcacheitem(containername, () =>
            {
                iunitycontainer unitycontainer = new unitycontainer();
                execonfigurationfilemap filemap = new execonfigurationfilemap
                {
                    execonfigfilename = path.combine(appdomain.currentdomain.basedirectory + @"configfiles\unity.config")
                };
                configuration configuration = configurationmanager.openmappedexeconfiguration(filemap, configurationuserlevel.none);
                unityconfigurationsection configsection = (unityconfigurationsection)configuration.getsection(unityconfigurationsection.sectionname);
                configsection.configure(unitycontainer, containername);
                return unitycontainer;
            }, timespan.fromminutes(30), null);

            return container.resolve<t>(alisname);
        }
    }

 

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