.NET Core 依赖注入以注入多个依赖项

Question

我正在尝试使用 .NET 核心依赖注入，但不明白如何为我的场景注入依赖。我有一个界面

   public interface IDataProvider()
   {
     public int GetData()
    }

这个接口由两个类实现

   public class GoldCustomer:IDataProvider
     {
      public int  GetData()
          {
               //implementation for gold customer
          }
       }

另一个类

     public class SilverCustomer:IDataProvider
     {
      public int  GetData()
          {
               //implementation for silver customer
          }
       }

现在我正在尝试配置依赖项

   public void ConfigureServices(IServiceCollection services)
     {
       //here i want to inject either gold customer or silver customer based on the scenario
        services.AddTransient<IDataProvider, GoldCustomer>();
     }

是否可以根据某些条件注入依赖？

Answer 1

为 GoldCustomer 和 SilverCustomer 创建新界面。不需要在 IGoldCustomer 和 ISilverCustomer 中添加 GetData，因为它已经有 IDataProvider 的 GetData()。

public interface ISilverCustomer : IDataProvider
{
}

public interface IGoldCustomer : IDataProvider
{
}

然后在 Startup.cs 中注入依赖

services.AddTransient<IGoldCustomer, GoldCustomer>();
services.AddTransient<ISilverCustomer, SilverCustomer>();

Answer 2

我希望您在应用依赖注入后尝试实现@Asherguru 答案所证明的目标，或者您可以应用下图所示的策略模式示例

namespace DemoInject.Services
{
   public interface IStrategy
    {
        public int GetData();
    }
}


namespace DemoInject.Services
{
    public interface IDiamondCustomer: IStrategy
    {       
    }
    public class DiamondCustomer : IDiamondCustomer
    {
        public int GetData()
        {
            return 5000;
        }
    }
}

namespace DemoInject.Services
{
    public interface ISilverCustomer: IStrategy
    {       
    }
    public class SilverCustomer : ISilverCustomer
    {
        public int GetData()
        {
            return 2000;
        }
    }
}

开课时

  // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddTransient<IDiamondCustomer, DiamondCustomer>();
            services.AddTransient<ISilverCustomer, SilverCustomer>();      
            services.AddControllers();
        }

在控制器上

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using DemoInject.Services;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;

namespace DemoInject.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class WeatherForecastController : ControllerBase
    {
     
        private static readonly string[] Summaries = new[]
        {
            "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
        };

        private readonly ILogger<WeatherForecastController> _logger;
        private IStrategy strategy;
        private IDiamondCustomer diamondCustomer;
        private ISilverCustomer silverCustomer;

        public WeatherForecastController(ILogger<WeatherForecastController> logger, IDiamondCustomer diamondCustomer, ISilverCustomer silverCustomer)
        {
            _logger = logger;
            this.diamondCustomer = diamondCustomer;
            this.silverCustomer = silverCustomer;
        }

        [HttpGet("CheckOperation/{Id}")]
        public int CheckOperation(int Id)
        {
            //Basically identify customer if a is even then silver else diamond
            if (Id % 2 == 0)
            {
                this.strategy = this.silverCustomer;
            }
            else
            {
                this.strategy = this.diamondCustomer;
            }
            return this.strategy.GetData();
        }

        [HttpGet]
        public IEnumerable<WeatherForecast> Get()
        {
            var rng = new Random();
            return Enumerable.Range(1, 5).Select(index => new WeatherForecast
            {
                Date = DateTime.Now.AddDays(index),
                TemperatureC = rng.Next(-20, 55),
                Summary = Summaries[rng.Next(Summaries.Length)]
            })
            .ToArray();
        }
    }
}

使用偶数调用 CheckOperation 将导致 Silver 调用，而 Diamond 调用 else

Answer 3

你可以将这两个类的依赖注入到项目中，然后你可以把你当前项目需要用到的参数GoldCustomer或者SilverCustomer放到appsetting.json文件中，然后通过获取appsetting的参数来决定哪个类获取返回的数据。

在 appsetting.json 文件中：

  "AppSettings": {
    "CurrentCustomer": "SilverCustomer"
  }

创建此类以从 appsetting.json 文件中获取值：

 public class AppSettings
        {
            public string CurrentCustomer { get; set; }
        }

在 startup.cs 中注入 IDataProvider 和 AppSettings ：

  services.Configure<AppSettings>(Configuration.GetSection("AppSettings"));
            services.AddScoped<IDataProvider, GoldCustomer>();
            services.AddScoped<IDataProvider, SilverCustomer>();

这是课程：

public interface IDataProvider
    {
        public int GetData();
    }
    public class GoldCustomer : IDataProvider
    {
        public int GetData()
        {
            return 100;
        }
    }
    public class SilverCustomer : IDataProvider
    {
        public int GetData()
        {
            return 200;
        }
    }

控制器：

      public class HomeController : Controller
        {
            private readonly IEnumerable<IDataProvider> _dataProviders; 
            private AppSettings AppSettings { get; set; }
            public HomeController(MyDbContext context, IEnumerable<IDataProvider> dataProviders, IOptions<AppSettings> settings)
            { 
                _dataProviders = dataProviders;
                AppSettings = settings.Value;
            }
            public IActionResult Index()
            {
// this will get the data 200 which returned by SilverCustomer because the AppSettings.CurrentCustomer is SilverCustomer 
                var message = _dataProviders.FirstOrDefault(h => h.GetType().Name == AppSettings.CurrentCustomer)?.GetData();

            }
    }

更多详情，也可以参考this。

这是测试结果：