c# - 从类库项目访问 appsettings.json 文件设置

Question

我知道如何在 Web 项目上设置 appsettings.json 文件。但是你能告诉我如何从类库项目访问它吗？

我可以在 Web 项目中如下所示配置它。那么如何从类库项目中访问该值？这可能吗？

public class MyConfig
{
    public string ApplicationName { get; set; }
    public int Version { get; set; }
}

public class Startup 
{
    public IConfigurationRoot Configuration { get; set; }

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

        Configuration = builder.Build();
    }
}

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<MyConfig>(Configuration);
}

public class HomeController : Controller
{
    private readonly IOptions<MyConfig> config;

    public HomeController(IOptions<MyConfig> config)
    {
        this.config = config;
    }

    // GET: /<controller>/
    public IActionResult Index() => View(config.Value);
}

Answer 1

需要获取section然后绑定(bind)，改这个

// Add our Config object so it can be injected
services.Configure<MyConfig>(Configuration);

至

// Add our Config object so it can be injected
services.Configure<MyConfig>(option => Configuration.GetSection("MyConfig").Bind(option));

然后您将在 HomeController 或您注入(inject)它的任何其他地方获得值。

public class HomeController : Controller
{

    private readonly IOptions<MyConfig> config;

    public HomeController(IOptions<MyConfig> config)
    {
        this.config = config;
    }

    public IActionResult Index()
    {
        var value = config.Value.ApplicationName;
        var vars = config.Value.Version;
        return View();
    }
}

appsettings.json

{
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  },
  "MyConfig": {
    "ApplicationName": "My Application Name",
    "Version": 1
  }
}

我们如何称呼这个不同于 Web 的项目？

Asp.Net Core DI 在创建 Controller 之前解析所有依赖项。所以，我们可以创建一个接口(interface)并实现它。然后我们可以将它注入(inject) Controller 并从那里访问 appsettings.json 设置。

ICategory.cs

public interface ICategory
{
    IOptions<MyConfig> config;
    IQueryable<Categories> Get();
}

Category.cs

public class Category : ICategory
{
       private readonly IOptions<MyConfig> config;

       public Category(IOptions<MyConfig> config)
       {
            this.config = config;
       }
       public Categories Get(long id)
       {
            var value = config.Value.ApplicationName;
            var vars = config.Value.Version;
            return category;
      }
}

CategoryController.cs

public CategoriesController(ICategory category)
{
   this.category = category;
}

当我们调用 category.Get() 方法时，我们可以访问该方法中的 appsettings.json 设置。

在Startup.cs的ConfigureServices方法中注册

services.AddTransient<ICategory, Category>();