从.net核心中的appsettings.json获取价值

问题描述

不确定我在这里缺少什么，但无法从.net核心应用程序中的appsettings.json获取值.我的appsettings.json为:

Not sure what am I missing here but I am not able to get the values from my appsettings.json in my .net core application. I have my appsettings.json as:

{
    "AppSettings": {
        "Version": "One"
    }
}

启动:

public class Startup
{
    private IConfigurationRoot _configuration;
    public Startup(IHostingEnvironment env)
    {
        _configuration = new ConfigurationBuilder()
    }
    public void ConfigureServices(IServiceCollection services)
    {
      //Here I setup to read appsettings
      services.Configure<AppSettings>(_configuration.GetSection("AppSettings"));
    }
}

型号:

public class AppSettings
{
    public string Version{ get; set; }
}

控制器:

public class HomeController : Controller
{
    private readonly AppSettings _mySettings;

    public HomeController(IOptions<AppSettings> settings)
    {
        //This is always null
        _mySettings = settings.Value;
    }
}

_mySettings始终为空.这里有我想念的东西吗?

_mySettings is always null. Is there something that I am missing here?

推荐答案

程序和启动类

.NET Core 2.x

您不需要在Startup构造函数中新建IConfiguration.它的实现将由DI系统注入.

Program and Startup class

.NET Core 2.x

You don't need to new IConfiguration in the Startup constructor. Its implementation will be injected by the DI system.

// Program.cs
public class Program
{
    public static void Main(string[] args)
    {
        BuildWebHost(args).Run();
    }

    public static IWebHost BuildWebHost(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>()
            .Build();
}

// Startup.cs
public class Startup
{
    public IHostingEnvironment HostingEnvironment { get; private set; }
    public IConfiguration Configuration { get; private set; }

    public Startup(IConfiguration configuration, IHostingEnvironment env)
    {
        this.HostingEnvironment = env;
        this.Configuration = configuration;
    }
}

.NET Core 1.x

您需要告诉Startup加载appsettings文件.

.NET Core 1.x

You need to tell Startup to load the appsettings files.

// Program.cs
public class Program
{
    public static void Main(string[] args)
    {
        var host = new WebHostBuilder()
            .UseKestrel()
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseIISIntegration()
            .UseStartup<Startup>()
            .UseApplicationInsights()
            .Build();

        host.Run();
    }
}

//Startup.cs
public class Startup
{
    public IConfigurationRoot Configuration { get; private set; }

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

        this.Configuration = builder.Build();
    }
    ...
}

获取价值

有多种方法可以从应用程序设置中获取配置的值:

Getting Values

There are many ways you can get the value you configure from the app settings:

• 使用ConfigurationBuilder.GetValue<T>
的简单方法
• 使用 选项模式

• Simple way using ConfigurationBuilder.GetValue<T>
• Using Options Pattern

假设您的appsettings.json看起来像这样:

Let's say your appsettings.json looks like this:

{
    "ConnectionStrings": {
        ...
    },
    "AppIdentitySettings": {
        "User": {
            "RequireUniqueEmail": true
        },
        "Password": {
            "RequiredLength": 6,
            "RequireLowercase": true,
            "RequireUppercase": true,
            "RequireDigit": true,
            "RequireNonAlphanumeric": true
        },
        "Lockout": {
            "AllowedForNewUsers": true,
            "DefaultLockoutTimeSpanInMins": 30,
            "MaxFailedAccessAttempts": 5
        }
    },
    "Recaptcha": {
        ...
    },
    ...
}

简单方法

您可以将整个配置注入到控制器/类的构造函数中(通过IConfiguration)，并使用指定的键获取所需的值:

Simple Way

You can inject the whole configuration into the constructor of your controller/class (via IConfiguration) and get the value you want with a specified key:

public class AccountController : Controller
{
    private readonly IConfiguration _config;

    public AccountController(IConfiguration config)
    {
        _config = config;
    }

    [AllowAnonymous]
    public IActionResult ResetPassword(int userId, string code)
    {
        var vm = new ResetPasswordViewModel
        {
            PasswordRequiredLength = _config.GetValue<int>(
                "AppIdentitySettings:Password:RequiredLength"),
            RequireUppercase = _config.GetValue<bool>(
                "AppIdentitySettings:Password:RequireUppercase")
        };

        return View(vm);
    }
}

选项模式

如果您只需要从应用程序设置中选择一个或两个值，则ConfigurationBuilder.GetValue<T>效果很好.但是，如果您想从应用程序设置中获取多个值，或者不想在多个位置对这些键字符串进行硬编码，则使用 Options Pattern 可能会更容易.选项模式使用类来表示层次结构/结构.

Options Pattern

The ConfigurationBuilder.GetValue<T> works great if you only need one or two values from the app settings. But if you want to get multiple values from the app settings, or you don't want to hard code those key strings in multiple places, it might be easier to use Options Pattern. The options pattern uses classes to represent the hierarchy/structure.

要使用选项模式:

1. 定义代表结构的类
2. 注册那些类绑定到的配置实例
3. 将IOptions<T>注入要在其上获取值的控制器/类的构造函数中

1. Define classes to represent the structure
2. Register the configuration instance which those classes bind against
3. Inject IOptions<T> into the constructor of the controller/class you want to get values on

1.定义配置类以表示结构

您可以使用与应用设置中的键完全匹配的属性来定义类.类的名称不必与应用程序设置中的部分名称匹配:

1. Define configuration classes to represent the structure

You can define classes with properties that need to exactly match the keys in your app settings. The name of the class does't have to match the name of the section in the app settings:

public class AppIdentitySettings
{
    public UserSettings User { get; set; }
    public PasswordSettings Password { get; set; }
    public LockoutSettings Lockout { get; set; }
}

public class UserSettings
{
    public bool RequireUniqueEmail { get; set; }
}

public class PasswordSettings
{
    public int RequiredLength { get; set; }
    public bool RequireLowercase { get; set; }
    public bool RequireUppercase { get; set; }
    public bool RequireDigit { get; set; }
    public bool RequireNonAlphanumeric { get; set; }
}

public class LockoutSettings
{
    public bool AllowedForNewUsers { get; set; }
    public int DefaultLockoutTimeSpanInMins { get; set; }
    public int MaxFailedAccessAttempts { get; set; }
}

2.注册配置实例

然后您需要在启动时在ConfigureServices()中注册此配置实例:

2. Register the configuration instance

And then you need to register this configuration instance in ConfigureServices() in the start up:

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
...

namespace DL.SO.UI.Web
{
    public class Startup
    {
        ...
        public void ConfigureServices(IServiceCollection services)
        {
            ...
            var identitySettingsSection =
                _configuration.GetSection("AppIdentitySettings");
            services.Configure<AppIdentitySettings>(identitySettingsSection);
            ...
        }
        ...
    }
}

3.注入IOptions

最后在要获取值的控制器/类上，您需要通过构造函数注入IOptions<AppIdentitySettings>:

public class AccountController : Controller
{
    private readonly AppIdentitySettings _appIdentitySettings;

    public AccountController(IOptions<AppIdentitySettings> appIdentitySettingsAccessor)
    {
        _appIdentitySettings = appIdentitySettingsAccessor.Value;
    }

    [AllowAnonymous]
    public IActionResult ResetPassword(int userId, string code)
    {
        var vm = new ResetPasswordViewModel
        {
            PasswordRequiredLength = _appIdentitySettings.Password.RequiredLength,
            RequireUppercase = _appIdentitySettings.Password.RequireUppercase
        };

        return View(vm);
    }
}

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