asp.netcore选项Options模块的笔记

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这篇博客是写给自己看的。已经不止一次看到AddOptions的出现，不管是在.net core源码还是别人的框架里面，都充斥着AddOptions。于是自己大概研究了下，没有深入，因为，我的功力还是不够，等能力到了再回头研究下。在这里还是要说一遍，因为DI的重要性不言而喻，不必谈的太深，说下自己的理解:

DI实现其实很简单，首先设计类来实现接口，而不是把所有的程序逻辑写在一个类文件中，然后我们传入一个接口和一个继承自接口的类作为参数，然后我们在相应的函数那将泛型参数T作为形参，伪代码:

//调用部分

HandleDI<ITest, Test>

//实现部分

HandleDI<TInterface, T>

// 使用反射，EMIT，委托来实例化T创建TInterface的对象

然后我们使用反射或者EMIT或是委托TInterface对象。这就是DI的实现过程。

DI说白了，作用就是解耦的实例化继承自接口的类

如果在程序中基于IOptions<TOptions>实现了你自己的选项配置类，最好就是调用AddOptions完成Options的几个重要对象的实例化。

AddOptions:
完成几个重要的Options对象的实例化:

public static IServiceCollection AddOptions(this IServiceCollection services)
{
    if (services == null)
    {
        throw new ArgumentNullException(nameof(services));
    }

    services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptions<>), typeof(OptionsManager<>)));
    services.TryAdd(ServiceDescriptor.Scoped(typeof(IOptionsSnapshot<>), typeof(OptionsManager<>)));
    services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptionsMonitor<>), typeof(OptionsMonitor<>)));
    services.TryAdd(ServiceDescriptor.Transient(typeof(IOptionsFactory<>), typeof(OptionsFactory<>)));
    services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptionsMonitorCache<>), typeof(OptionsCache<>)));
    return services;
}

View Code

Configure: 完成的是TOption类的实例化过程，最终调用AddSingleton做DI。

/// <summary>
        /// Registers an action used to configure a particular type of options.
        /// Note: These are run before all <seealso cref="PostConfigure{TOptions}(IServiceCollection, Action{TOptions})"/>.
        /// </summary>
        /// <typeparam name="TOptions">The options type to be configured.</typeparam>
        /// <param name="services">The <see cref="IServiceCollection"/> to add the services to.</param>
        /// <param name="configureOptions">The action used to configure the options.</param>
        /// <returns>The <see cref="IServiceCollection"/> so that additional calls can be chained.</returns>
        public static IServiceCollection Configure<TOptions>(this IServiceCollection services, Action<TOptions> configureOptions) where TOptions : class
            => services.Configure(Options.Options.DefaultName, configureOptions);

        /// <summary>
        /// Registers an action used to configure a particular type of options.
        /// Note: These are run before all <seealso cref="PostConfigure{TOptions}(IServiceCollection, Action{TOptions})"/>.
        /// </summary>
        /// <typeparam name="TOptions">The options type to be configured.</typeparam>
        /// <param name="services">The <see cref="IServiceCollection"/> to add the services to.</param>
        /// <param name="name">The name of the options instance.</param>
        /// <param name="configureOptions">The action used to configure the options.</param>
        /// <returns>The <see cref="IServiceCollection"/> so that additional calls can be chained.</returns>
        public static IServiceCollection Configure<TOptions>(this IServiceCollection services, string name, Action<TOptions> configureOptions)
            where TOptions : class
        {
            if (services == null)
            {
                throw new ArgumentNullException(nameof(services));
            }

            if (configureOptions == null)
            {
                throw new ArgumentNullException(nameof(configureOptions));
            }

            services.AddOptions();
            services.AddSingleton<IConfigureOptions<TOptions>>(new ConfigureNamedOptions<TOptions>(name, configureOptions));
            return services;
        }