ASP.NET Core 6.0 ServiceCollection 实现依赖注入

标签：Core microphone1 ASP Console ServiceCollection IMicrophone serviceDescriptors Wr

ASP.NET Core6 lOC容器

控制反转（Inversion of Control, IoC）是一种软件设计模式，其目的是降低代码之间的耦合度。在C#中，可以使用依赖注入（Dependency Injection, DI）来实现控制反转。

一般系统分为 UI 层、BLL 层、DAL 层、IBLL 层和 IDAL 层，IOC 实质是通过抽象 IBLL（接口、抽象类、普通父类）获取BLL层的实例，如果使用依赖注入，那么各层的关系如下：

内置容器 ServiceCollection 的应用

新建 Learn.NET6.Business.Interfaces 类库，新建 IMicrophone接口：

    public interface IMicrophone
    {

    }

在 Learn.NET6.ExceptionService 层添加 Microphone 类：

    public class Microphone : IMicrophone
    {
        public Microphone()
        {
            Console.WriteLine($"{this.GetType().Name}被构造。。");
        }
    }

新建 Learn.NET6.DemoTest 控制台应用程序，在 Program 类中：

需要注意的是 ServiceCollection 只支持构造函数注入。

{
    //传统做法，创建一个实例
    Microphone microphone = new Microphone();
    IMicrophone microphone1 = new Microphone();

}

//内置容器：
{
    //1.创建一个容器
    //nuget 引入 Microsoft.Extensions.DependencyInjection
    ServiceCollection serviceDescriptors = new ServiceCollection();
    //2.注册抽象和具体普通类之间的关系
    serviceDescriptors.AddTransient<IMicrophone, Microphone>();
    //3. serviteDescriptors.builder
    ServiceProvider serviceProvider = serviceDescriptors.BuildServiceProvider();

    IMicrophone microphone = serviceProvider.GetService<IMicrophone>();
}

IOC容器-DI依赖注入

依赖注入

在创建对象的实例时，如果对象A，依赖于对象B,对象B依赖于对象C，那么在创建对象A的时候，

自动的把对象C创建出来交给对象B，再把对象B创建出来交给对象A，从而创建出对象A。

可以在全局跟一个ioc容器，配置抽象和具体普通之间的关系的时候，可以修改，这里修改了，获取实例就获取新的实例。

在 Learn.NET6.ExceptionService. 新建 AndroidPhone、ApplePhone、Headphone、Microphone、MicrophoneNew 和 Power 类，多个类且类之间互相引用：

public class AndroidPhone : IPhone
{
    public IMicrophone Microphone { get; set; }
    public IHeadphone Headphone { get; set; }
    public IPower Power { get; set; }

    public AndroidPhone()
    {
        Console.WriteLine("{0}构造函数", this.GetType().Name);
    }

    public void Call()
    {
        Console.WriteLine("{0}打电话", this.GetType().Name); ;
    }

    public void Init123456678890(IPower iPower)
    {
        Power = iPower;
    }

    public void Text()
    {
        Console.WriteLine("{0}发信息", this.GetType().Name); ;
    }

    public object QueryUser(object opara)
    {
        throw new NotImplementedException();
    }
}

public class ApplePhone : IPhone
{
    public IMicrophone Microphone { get; set; }
    public IHeadphone Headphone { get; set; }
    public IPower Power { get; set; }

    public ApplePhone(IHeadphone iHeadphone)
    {
        this.Headphone = iHeadphone;
        Console.WriteLine("{0}带参数构造函数", this.GetType().Name);
    }

    public virtual void Call()
    {
        Console.WriteLine("{0}打电话", this.GetType().Name); ;
    }

    public void Text()
    {
        Console.WriteLine("{0}发信息", this.GetType().Name); ;
    }


    public object QueryUser(object opara)
    {
        return new
        {
            Id = 123,
            Name = "Richard",
            DateTiem = DateTime.Now.ToString()
        };
    }


    public void Init123456678890(IPower iPower)
    {
        this.Power = iPower;
    }
}

    public class Headphone : IHeadphone
    {

        public Headphone(IPower power)
        {
            Console.WriteLine($"{this.GetType().Name}被构造。。");
        }

    }

    public class Microphone : IMicrophone
    {
        public Microphone()
        {
            Console.WriteLine($"{this.GetType().Name}被构造。。");
        }
    }

    public class MicrophoneNew : IMicrophone
    {
        public MicrophoneNew()
        {
            Console.WriteLine($"{this.GetType().Name}被构造。。");
        }
    }

    public class Power : IPower
    {
        private IMicrophone Microphone;
        private IMicrophone Microphone2;

        public Power(IMicrophone microphone)
        {
            Console.WriteLine($"{this.GetType().Name}被构造。。");
            this.Microphone = microphone;
        }

        public Power(int microphone)
        {
            Console.WriteLine($"{this.GetType().Name}被构造。。");
        }

        public Power(IMicrophone microphone, IMicrophone microphone2)
        {
            Console.WriteLine($"{this.GetType().Name}被构造。。");
            this.Microphone = microphone;
            this.Microphone2 = microphone2;
        }
    }

在 Learn.NET6.Business.Interfaces 新建 IHeadphone、IMicrophone、IPhone 和 IPower：

    public interface IHeadphone
    {

    }

    public interface IMicrophone
    {

    }

    public interface IPhone
    {
        void Call();

        void Text();

        void Init123456678890(IPower iPower);

        IMicrophone Microphone { get; set; }
        IHeadphone Headphone { get; set; }
        IPower Power { get; set; }
        object QueryUser(object opara);
    }

    public interface IPower
    {

    }

传统做法创建对象

{
    // 传统做法创建对象
    IMicrophone microphone = new Microphone();
    IPower power = new Power(microphone);
    IHeadphone headphone = new Headphone(power);
}

IOC容器支持依赖注入

{
    //IOC容器支持依赖注入
    ServiceCollection serviceDescriptors = new ServiceCollection();
    serviceDescriptors.AddTransient<IMicrophone, Microphone>();
    serviceDescriptors.AddTransient<IPower, Power>();
    serviceDescriptors.AddTransient<IHeadphone, Headphone>();
    ServiceProvider serviceProvider = serviceDescriptors.BuildServiceProvider();

    IHeadphone headphone = serviceProvider.GetService<IHeadphone>();
}

ServiceCollection 支持的生命周期

ServiceCollection--IOC容器本质就是来创建对象的；

那么在对象创建的时候，有些特殊的场景，需要创建出来的对象有的支持单例，有的在一些范围内支持单例，面对于这些诉求，ServiceCollection支持了三种生命周期来解决这个问题。

瞬时生命周期--Transient

//一、AddTransient：瞬时生命周期，每一次创建都是一个全新的实例
{
    ServiceCollection serviceDescriptors = new ServiceCollection();
    serviceDescriptors.AddTransient<IMicrophone, Microphone>();
    ServiceProvider serviceProvider = serviceDescriptors.BuildServiceProvider();
    IMicrophone microphone1 = serviceProvider.GetService<IMicrophone>();
    IMicrophone microphone2 = serviceProvider.GetService<IMicrophone>();
    IMicrophone microphone3 = serviceProvider.GetService<IMicrophone>();
    IMicrophone microphone4 = serviceProvider.GetService<IMicrophone>();
    // 比较内存的引用地址，如果相同就表示同一个对象，结果是不相同
    Console.WriteLine($"microphone1 比较 microphone2：{object.ReferenceEquals(microphone1, microphone2)}");
    Console.WriteLine($"microphone1 比较 microphone3：{object.ReferenceEquals(microphone1, microphone3)}");
    Console.WriteLine($"microphone2 比较 microphone4：{object.ReferenceEquals(microphone2, microphone4)}");

}

单例生命周期--Singleton

//一、AddSingleton：单例生命周期，每一次创建都是同一个实例
{
    ServiceCollection serviceDescriptors = new ServiceCollection();
    serviceDescriptors.AddSingleton<IMicrophone, Microphone>();
    ServiceProvider serviceProvider = serviceDescriptors.BuildServiceProvider();
    IMicrophone microphone1 = serviceProvider.GetService<IMicrophone>();
    IMicrophone microphone2 = serviceProvider.GetService<IMicrophone>();
    IMicrophone microphone3 = serviceProvider.GetService<IMicrophone>();
    IMicrophone microphone4 = serviceProvider.GetService<IMicrophone>();
    // 比较内存的引用地址，如果相同就表示同一个对象，结果是相同
    Console.WriteLine($"microphone1 比较 microphone2：{object.ReferenceEquals(microphone1, microphone2)}");
    Console.WriteLine($"microphone1 比较 microphone3：{object.ReferenceEquals(microphone1, microphone3)}");
    Console.WriteLine($"microphone2 比较 microphone4：{object.ReferenceEquals(microphone2, microphone4)}");
}

作用域生命周期--Scoped

//一、AddScoped：作用域生命周期，同一个serviceProvider获取到的是同一个实例
{
    ServiceCollection serviceDescriptors = new ServiceCollection();
    serviceDescriptors.AddScoped<IMicrophone, Microphone>();
    ServiceProvider serviceProvider1 = serviceDescriptors.BuildServiceProvider();
    IMicrophone microphone1 = serviceProvider1.GetService<IMicrophone>();
    IMicrophone microphone2 = serviceProvider1.GetService<IMicrophone>();

    ServiceProvider serviceProvider2 = serviceDescriptors.BuildServiceProvider();
    IMicrophone microphone3 = serviceProvider2.GetService<IMicrophone>();
    IMicrophone microphone4 = serviceProvider2.GetService<IMicrophone>();

    // 比较内存的引用地址
    Console.WriteLine($"microphone1 比较 microphone2：{object.ReferenceEquals(microphone1, microphone2)}"); //True
    Console.WriteLine($"microphone3 比较 microphone4：{object.ReferenceEquals(microphone3, microphone4)}"); //True
    Console.WriteLine($"microphone1 比较 microphone3：{object.ReferenceEquals(microphone1, microphone3)}"); //False
    Console.WriteLine($"microphone1 比较 microphone1：{object.ReferenceEquals(microphone1, microphone4)}"); //False
}

标签：Core,microphone1,ASP,Console,ServiceCollection,IMicrophone,serviceDescriptors,Wr
From： https://blog.csdn.net/nmmking/article/details/139207506