在 ASP.NET Core 的 ConfigureServices 阶段实际读取 AppSettings

Question

我需要在 ASP.NET Core 1.0 Web 应用程序的 ConfigureServices 方法中设置一些依赖项（服务）。

问题是基于新的 JSON 配置，我需要设置一个服务或其他服务。

我似乎无法真正阅读应用程序生命周期的ConfigureServices 阶段的设置：

public void ConfigureServices(IServiceCollection services)
{
    var section = Configuration.GetSection("MySettings"); // this does not actually hold the settings
    services.Configure<MySettingsClass>(section); // this is a setup instruction, I can't actually get a MySettingsClass instance with the settings
    // ...
    // set up services
    services.AddSingleton(typeof(ISomething), typeof(ConcreteSomething));
}

我需要真正阅读该部分并决定注册ISomething 的内容（可能与ConcreteSomething 不同）。

Answer 1

这就是您可以在ConfigureServices 方法中从appSettings.json 获取键入设置的方式：

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

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.Configure<MySettings>(Configuration.GetSection(nameof(MySettings)));
        services.AddSingleton(Configuration);

        // ...

        var settings = Configuration.GetSection(nameof(MySettings)).Get<MySettings>();
        int maxNumberOfSomething = settings.MaxNumberOfSomething;

        // ...
    }

    // ...
}

Answer 2

从 ASP.NET Core 2.0 开始，我们在构建 WebHost 实例时在 Program 类中进行配置设置。此类设置示例：

return new WebHostBuilder()
    .UseKestrel()
    .UseContentRoot(Directory.GetCurrentDirectory())
    .ConfigureAppConfiguration((builderContext, config) =>
    {
        IHostingEnvironment env = builderContext.HostingEnvironment;

        config.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
            .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);
    })

其中，这允许直接在Startup 类中使用配置，通过构造函数注入获取IConfiguration 的实例（谢谢，内置 DI 容器）：

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

    public IConfiguration Configuration { get; }

    ...
}

Answer 3

您可以通过Configuration["ConfigSection:ConfigValue"]) 访问 appsettings.json 值

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

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<MyContext>(o => 
            o.UseSqlServer(Configuration["AppSettings:SqlConn"]));
    }
}

appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Warning",
      "System": "Information",
      "Microsoft": "Warning"
    }
  },
  "AppSettings": {
    "SqlConn": "Data Source=MyServer\\MyInstance;Initial Catalog=MyDb;User ID=sa;Password=password;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False;"
  }
}

Answer 4

appsettings.json 文件：

  "MyApp": {
    "Jwt": {
      "JwtSecretConfigKey": "jwtSecretConfigKey",
      "Issuer": "appIssuer",
      "Audience": "appAudience",
      "ExpireMinutes": 60
    }
  }

添加一个类来绑定“MyApp”的Jwt部分 ...

   public class JwtConfig
    {
        public string JwtSecretConfigKey { get; set; }
        public string Issuer { get; set; }
        public string Audience { get; set; }
        public int ExpireMinutes { get; set; }
    }

在 ConfigureServices 方法中：

//reading config from appsettings.json
var jwtConfig = Configuration.GetSection("MyApp:Jwt").Get<JwtConfig>();

//using config data ....
services.AddJwt(new AddJwtOptions(jwtConfig.JwtSecretConfigKey, jwtConfig.Issuer, jwtConfig.Audience, jwtConfig.ExpireMinutes));

下面的代码和上面的一样。它也有效...

var jwtConfig = Configuration.GetSection("MyApp").GetSection("Jwt").Get<JwtConfig>();

希望这会有所帮助..

Answer 5

尝试下一个：

var settings = new MySettings();
Configuration.GetSection(nameof(MySettings)).Bind(settings);