.NET Core中多IHostedService实例的不同构造参数注入问题

问题背景 #

你当前的场景是：有4台相同设备，需通过TCP连接（每台对应独立IP）通信并获取参数；已经实现了继承自BackgroundService的RemoteDevice类，构造函数为：

public RemoteDevice(RemoteDeviceConfig config, ILogger<RemoteDevice> logger)

类内通过ExecuteAsync方法的while{}循环处理业务逻辑。现在希望基于配置文件构建Worker Service，创建多个RemoteDevice实例，但在Program.cs中多次调用services.AddHostedService<RemoteDevice>()时，发现移除RemoteDeviceConfig时ILogger能正常注入，添加该配置类后却不知如何正确注入。使用的技术栈是.NET Core 3.0 + VS2019 + Worker Service模板项目。

已采纳的解决方案 #

采纳了@gldraphael的方案，核心思路是通过主Worker类统一管理多设备实例，同时借助ILoggerFactory为每个设备实例创建独立的日志实例，从配置文件批量加载所有设备的配置项。

代码示例 #

Worker.cs 主服务类

using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

public class Worker : BackgroundService
{
    private readonly ILogger<Worker> _logger;
    private readonly ILoggerFactory _loggerFactory;
    private readonly List<DeviceConfig> _config;
    private List<DeviceMainClass> _devices;

    public Worker(IOptions<List<DeviceConfig>> options, ILogger<Worker> logger, ILoggerFactory loggerFactory)
    {
        _config = options.Value;
        _logger = logger;
        _loggerFactory = loggerFactory;
        _devices = new List<DeviceMainClass>();

        // 遍历配置，逐个创建设备实例
        foreach (var deviceConfig in _config)
        {
            _devices.Add(new DeviceMainClass(
                _loggerFactory.CreateLogger<DeviceMainClass>(),
                deviceConfig
                // 可在此添加其他需要注入的参数
            ));
        }
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            _logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
            await Task.Delay(1000, stoppingToken);
        }
    }
}

DeviceMainClass（原RemoteDevice类调整）

using Microsoft.Extensions.Logging;
using System.Threading;
using System.Threading.Tasks;

public class DeviceMainClass : BackgroundService
{
    private readonly ILogger<DeviceMainClass> _logger;
    private readonly DeviceConfig _deviceConfig;

    public DeviceMainClass(ILogger<DeviceMainClass> logger, DeviceConfig deviceConfig)
    {
        _logger = logger;
        _deviceConfig = deviceConfig;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        // 单台设备的TCP通信、参数获取逻辑写在这里
        while (!stoppingToken.IsCancellationRequested)
        {
            _logger.LogInformation("Device {deviceIp} running at: {time}", 
                _deviceConfig.IpAddress, DateTimeOffset.Now);
            // 执行设备专属业务操作
            await Task.Delay(5000, stoppingToken);
        }
    }
}

配置与启动说明 #

1. 配置文件（appsettings.json）：添加多设备的配置项

{
  "DeviceConfig": [
    {
      "IpAddress": "192.168.1.101",
      "Port": 8080
    },
    {
      "IpAddress": "192.168.1.102",
      "Port": 8080
    },
    {
      "IpAddress": "192.168.1.103",
      "Port": 8080
    },
    {
      "IpAddress": "192.168.1.104",
      "Port": 8080
    }
  ]
}

2. Program.cs 配置绑定：

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureServices((hostContext, services) =>
            {
                // 将配置文件中的DeviceConfig节点绑定到List<DeviceConfig>
                services.Configure<List<DeviceConfig>>(
                    hostContext.Configuration.GetSection("DeviceConfig"));
                // 注册主Worker服务
                services.AddHostedService<Worker>();
            });
    }
}

通过这套方案，就能基于配置文件批量创建设备实例，每个实例都拥有独立的配置和日志记录，完美解决你之前遇到的依赖注入问题。

内容的提问来源于stack exchange，提问作者Simon