将子选项数组中的 IOptions 注入服务

Question

I have a web service that posts data to a variety of different external servers, with a specific server to use specified by the incoming data to my API. New servers could be added at any time.

I have an appSettings.json like this:

"Settings": {
  "SomeSetting1": "Value",
  "SomeSetting2": "Value",
  "ExternalServers": [
    {
      "Name": "ServerA",
      "Address": "ServerAAddress"
    },
    ...
    {
      "Name": "ServerZ",
      "Address": "ServerZAddress"
    },
  ]
}

With the following support classes:

public class MySettings {
    public string SomeSetting1 { get; set; }
    public string SomeSetting2 { get; set; }
    public List<ExternalServerSettings> ExternalServers { get; set; } 
}

public class ExternalServerSettings {
    public string Name { get; set; }
    public string Address { get; set; }
}

I am injecting the full Settings in Startup.cs:

services.Configure<MySettings>(mySettings => Configuration.GetSection("Settings").Bind(mySettings));

I am creating a new service that I only want to inject an instance of ExternalServerSettings .

Currently I am doing this:

public class MyService : IMyService
{
    private readonly ExternalServerSettings ServerSettings;

    public MyService(ExternalServerSettings serverSettings) {
        ServerSettings = serverSettings
    }
}

In my controller or another service I will select the specific server based on inputs to the Post method.

But previously I have created other services which are injecting settings with IOptions :

public OtherService(IOptions<MySettings> mySettings)

//instead of...
public OtherService(MySettings mySettings)

The existential crisis I am having is that I am creating MyService knowing in advance that I would be selecting and injecting a specific object instead of using IOptions, but best practices dictate that I shouldn't know/care what is happening externally, and I would like to be able to create any Services consistently without worrying how they may be called. Is my pattern OK or is there a way to do this while still utilizing IOptions ?

I am very new C# web API and dependency injection, and I just want to make sure that I am following best practices for when I move to more complex projects.

Answer 1

Below is a work demo, you can refer to it.

TopItemSettings

public class TopItemSettings
    {
        public const string Month = "Month";
        public const string Year = "Year";

        public string Name { get; set; }
        public string Model { get; set; }
    }

Put below into appsetting.json

"TopItem": {
    "Month": {
      "Name": "Green Widget",
      "Model": "GW46"
    },
    "Year": {
      "Name": "Orange Gadget",
      "Model": "OG35"
    }
  }

Register month in the startup

 public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.Configure<TopItemSettings>(TopItemSettings.Month,
                                      Configuration.GetSection("TopItem:Month"));
            
            
            //services.Configure<TopItemSettings>(TopItemSettings.Year,
            //                                    Configuration.GetSection("TopItem:Year"));
            services.AddControllers();
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "OPtions", Version = "v1" });
            });
        }

ValuesController

[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
    private readonly TopItemSettings _monthTopItem;
    public ValuesController(IOptionsSnapshot<TopItemSettings> namedOptionsAccessor)
    {
        _monthTopItem = namedOptionsAccessor.Get(TopItemSettings.Month);
    }
    public ContentResult OnGet()
    {
        return Content($"Month:Name {_monthTopItem.Name} \n" +
                       $"Month:Model {_monthTopItem.Model} \n\n");
    }
}

Result: