C# DI依赖注入的实现示例

using Microsoft.Extensions.DependencyInjection;
using System;

namespace ioc1
{
    class Program
    {
        static void Main(string[] args)
        {
            ServiceCollection services = new ServiceCollection();
            //每次请求获取都是新的对象实例
            services.AddTransient<ITestService, TestServiceImpl>();
            //每次在一个生命周期中请求获取的都是同一个对象
            services.AddSingleton<TestServiceImpl2>();
            //同一个范围内获取的是同一个对象范围指“{}”再统一个大括号中的对象
            services.AddScoped<TestServiceImpl3>();
            using( ServiceProvider sp = services.BuildServiceProvider())
            {
                //GetService如果找不到服务，就返回null
                //GetRequiredService:必须的，如果找不到就报异常
                //GetServices找到服务的集合；
                ITestService t = sp.GetService<ITestService>();
                t.Name = "白沙王";
                t.SayHi();
                ITestService t1 = sp.GetService<ITestService>();
                Console.WriteLine(t.GetType());
                Console.WriteLine(object.ReferenceEquals(t,t1));
                t1.Name = "喜马拉雅";
                t1.SayHi();
                Console.WriteLine("----------------------");
                TestServiceImpl2 t2 = sp.GetService<TestServiceImpl2>();
                t2.Name = "白沙王";
                t2.SayHi();
                TestServiceImpl2 t21 = sp.GetService<TestServiceImpl2>();
                Console.WriteLine(object.ReferenceEquals(t2, t21));
                t21.Name = "喜马拉雅";
                t21.SayHi();
                t2.SayHi();
                Console.WriteLine("----------------------");
                using (IServiceScope scope1 = sp.CreateScope())
                {
                    //再scope中获取scope相关对象，scope.ServiceProvider而不是sp
                    TestServiceImpl3 t3 = scope1.ServiceProvider.GetService<TestServiceImpl3>();
                    t3.Name = "白沙王";
                    t3.SayHi();
                    TestServiceImpl3 t33 = scope1.ServiceProvider.GetService<TestServiceImpl3>();
                    t33.Name = "喜马拉雅";
                    t33.SayHi();
                    Console.WriteLine(object.ReferenceEquals(t3, t33));
                }
            }
                Console.ReadKey();
        }
    }
    interface ITestService
    {
        string Name { get; set; }
        void SayHi();
    }
    public class TestServiceImpl : ITestService
    {
        public string Name { get; set; }

        public void SayHi()
        {
            Console.WriteLine($"Hi,i'm{Name}");
        }

    }

    public class TestServiceImpl2 : ITestService
    {
        public string Name { get; set ; }

        public void SayHi()
        {
            Console.WriteLine($"你好，我是{Name}");
        }
    }


    public class TestServiceImpl3 : ITestService
    {
        public string Name { get; set; }

        public void SayHi()
        {
            Console.WriteLine($"you good，我是{Name}");
        }
    }
}

services.AddSingleton<TestServiceImpl2>();