Microsoft.Extensions.DependencyInjection.Abstractions
Microsoft.Extensions.DependencyInjection　

//声明一个接口
public interface IVipService    
{}
//声明IVipService接口的实现类
public class VipService : IVipService 
{}　

public void ConfigureServices(IServiceCollection services)
{
    services.AddScoped<IVipService, VipService>();
    services.AddControllers();
}

[Route("[controller]")]
public class WeatherForecastController : ControllerBase
{
    private readonly IVipService _vipService;

    public WeatherForecastController( IVipService vipService)  //在构造函数中注入IVipService接口
    {
        _vipService = vipService;
    }

    [HttpGet]
    public string Get( )
    {
        return _vipService.GetHashCode().ToString();
    }
}

[Route("[controller]")]
public class WeatherForecastController : ControllerBase
{

    [HttpGet]
    public string Get([FromServices]IVipService vipService)  // 在方法入参中使用[FromServices]特性注入IVipService接口
    {
        return vipService.GetHashCode().ToString();
    }
}　　

public enum ServiceLifetime
{
    // 单例模式
    Singleton = 0,
    // 作用域模式
    Scoped = 1,
    // 瞬时模式
    Transient = 2
}

三种生命周期，使用下面三种不同的方法注入
services.AddSingleton<IVipService, VipService>();
services.AddScoped<IVipService, VipService>();
services.AddTransient<IVipService, VipService>();

services.AddSingleton(typeof(IVipService<>),typeof(VipService<>)); 

//一个接口 两个实现类 
public interface IVipService
{
}

public class ErpVipService : IVipService
{
}

public class WxVipService : IVipService
{
}
//将工厂包装一层
public class VipServiceFactory
{
    private readonly Func<int, IVipService> _func;
    public VipServiceFactory(Func<int, IVipService> func)
    {
        _func = func;
    }
    public IVipService GetInstence(int type)
    {
        return _func(type);
    }
}
//注入扩展类
public static class VipServiceExtensions
{
    public static IServiceCollection AddVipService(this IServiceCollection services)
    {
        services.AddScoped<ErpVipService>();
        services.AddScoped<WxVipService>();
        //通过工厂方式根据类型条件决定创建哪个实现类
        services.AddScoped(serviceProvider =>
        {
            Func<int, IVipService> func = type =>
            {
                if (type == 0) return (IVipService)serviceProvider.GetService<ErpVipService>();
                else
                    return (IVipService)serviceProvider.GetService<WxVipService>();
            };
            return func;
        });
        services.AddScoped<VipServiceFactory>();
        return services;
    }
}

public void ConfigureServices(IServiceCollection services)
{
    services.AddVipService();
    services.AddControllers();
}

[Route("[controller]")]
public class WeatherForecastController : ControllerBase
{
    private readonly VipServiceFactory _vipServiceFactory;
    
    //将工厂类注入到构造函数
    public WeatherForecastController(VipServiceFactory vipServiceFactory)
    {
        _vipServiceFactory = vipServiceFactory;
    }

    [HttpGet]
    public string Get( )
    {
      return   _vipServiceFactory.GetInstence(0).GetHashCode().ToString();
    }
}