c# - 将 IOptions 传递到 .Net 核心中间件类以进行 json 配置检索

Question

我正在尝试根据 Options pattern 使用强类型的 json 配置设置在 .net 核心中。到目前为止的所有示例都显示了将强类型设置类注入(inject) Controller 是多么容易，但我需要在中间件类中使用它(非常类似于 this question，但在尝试之后我没有进一步推进)。

那么，设置:

mysettings.json

{
  "MySettings": {
    "Name": "Some Name from config",
    "Description": "Some Description from config"
  }
}

mysettings.cs

public class MySettings
{
    public string Name { get; set; } = "Default name";

    public string Description { get; set; } = "Default description";
}

startup.cs

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    // Add functionality to inject IOptions<T>
    services.AddOptions();

    // Add our Config object so it can be injected
    services.Configure<MySettings>(Configuration.GetSection("MySettings"));
    services.AddSingleton<IMySettingsService, MySettingsService>();
}

MysettingsService.cs

public class MysettingsService : IMysettingsService
{
    private MySettings mySettings { get; set; }

    public MysettingsService (MySettings _mySettings)
    {
        mySettings = _mySettings.value;
    }

    public string GetName()
    {
        return mySettings.Name; 
    }
}

我如何着手实例化 MysettingsService.cs 并注入(inject) IOptions<MySettings>进入类构造函数以便调用 GetName 方法？

Answer 1

几点:

• 提到的类中缺少构造函数 - MysettingsService
• 您是否在Startup 类中注册了IMysettingsService 的实现？
• 在注册实现时，您可以初始化 MysettingsService，如下所示: services.AddSingleton<IMysettingsService, MysettingsService >(i => new MysettingsService ());

按照以下步骤:

• 确保您已在 ConfigurationBuilder 中注册您的 JSON 文件 - mysettings.json

• 定义MySettings

  public class MySettings
  {
      public string Name { get; set; }
  
      public string Description { get; set; }
  }
  

• 定义MySettingsService

  public class MySettingsService : IMySettingsService
  {
      private readonly MySettings mySettings;
  
      public MySettingsService (IOptions<MySettings> _mySettings)
      {
          mySettings = _mySettings.Value;
      }
  
      public string GetName()
      {
          return mySettings.Name; 
      }
  }
  

• 在启动中

  services.Configure<MySettings>(this.Configuration.GetSection("MySettings"));
  services.AddSingleton<IMySettingsService, MySettingsService >();
  

已编辑——我包括了供您遵循的实现

我已经创建了一个示例应用程序，它适用于我；请按照以下步骤操作:

一些细节。我的申请名称是:SettingsApp

1. 创 build 置文件 - mySettings.json - 内容

{
  "MySettings": {
    "Name": "Some Name from config",
    "Description": "Some Description from config"
  }
}

1. 在 Startup 中配置它

public Startup(IHostingEnvironment env)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("mySettings.json", true, reloadOnChange: true)
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
        .AddEnvironmentVariables();

    if (env.IsDevelopment())
    {
        // This will push telemetry data through Application Insights pipeline faster, allowing you to view results immediately.
        builder.AddApplicationInsightsSettings(developerMode: true);
    }
    Configuration = builder.Build();
}

查看行:

.AddJsonFile("mySettings.json", true, reloadOnChange: true)

1. 创建 MySettings对象来保存设置

namespace SettingsApp.Initialisations
{
    public class MySettings
    {
        public string Name { get; set; }

        public string Description { get; set; }
    }
}

注意:我使用命名空间 SettingsApp.Initialisations来保存这个文件。您可以根据您的应用程序结构选择任何一个。

1. 创建界面IMySettingsService

namespace SettingsApp.Services
{
    public interface IMySettingsService
    {
        string GetName();
    }
}

注意:我使用命名空间 SettingsApp.Services为此。

1. 实现接口(interface) - IMySettingsService

using SettingsApp.Initialisations;
using Microsoft.Extensions.Options;

namespace SettingsApp.Services
{
    public class MySettingsService : IMySettingsService
    {
        private readonly MySettings mySettings;

        public MySettingsService(IOptions<MySettings> _mySettings)
        {
            mySettings = _mySettings.Value;
        }

        public string GetName()
        {
            return mySettings.Name;
        }
    }
}

1. 添加选项并让系统知道您在 Startup.ConfigureServices 中的实现方法

// This method gets called by the run time. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    // Options
    services.AddOptions();
    services.Configure<MySettings>(this.Configuration.GetSection("MySettings"));
    services.AddSingleton<IMySettingsService, MySettingsService>();

    // Add framework services.
    services.AddApplicationInsightsTelemetry(Configuration);

    services.AddMvc();
}

注意包括所需的使用。

检查下面的代码，了解这是如何完成的:

// Options
services.AddOptions();
services.Configure<MySettings>(this.Configuration.GetSection("MySettings"));
services.AddSingleton<IMySettingsService, MySettingsService>();

1. 使用实现(我正在使用 HomeController 进行测试。)

public class HomeController : Controller
{
    private IMySettingsService mySettingsService;

    public HomeController(IMySettingsService settingsService)
    {
        mySettingsService = settingsService;
    }

    public IActionResult Index()
    {
        // Get the settings
        var name = mySettingsService.GetName();

        return View();
    }

...

1. 查看结果: