如何从ASP.NET Core中的.json文件读取AppSettings值 [英] How to read AppSettings values from a .json file in ASP.NET Core

问题描述

我已经在文件appsettings / Config .json中设置了我的AppSettings数据，如下所示：

I have set up my AppSettings data in file appsettings/Config .json like this:

{
  "AppSettings": {
        "token": "1234"
    }
}

我已经在网上搜索了如何从.json文件中读取AppSettings值的信息，但没有得到任何有用的信息。

I have searched online on how to read AppSettings values from .json file, but I could not get anything useful.

我尝试过：

var configuration = new Configuration();
var appSettings = configuration.Get("AppSettings"); // null
var token = configuration.Get("token"); // null

我知道使用ASP.NET 4.0可以做到：

I know with ASP.NET 4.0 you can do this:

System.Configuration.ConfigurationManager.AppSettings["token"];

但是如何在ASP.NET Core中做到这一点？

But how do I do this in ASP.NET Core?

推荐答案

这有些曲折。我已修改此答案以使其与 ASP.NET Core 2.0 保持最新（截至2018年2月26日）。

This has had a few twists and turns. I've modified this answer to be up to date with ASP.NET Core 2.0 (as of 26/02/2018).

此大部分取自官方文档：

要使用ASP.NET应用程序中的设置，建议仅在应用程序的中实例化配置启动类。然后，使用选项模式访问各个设置。假设我们有一个 appsettings.json 文件，如下所示：

To work with settings in your ASP.NET application, it is recommended that you only instantiate a Configuration in your application’s Startup class. Then, use the Options pattern to access individual settings. Let's say we have an appsettings.json file that looks like this:

{
  "MyConfig": {
   "ApplicationName": "MyApp",
   "Version": "1.0.0"
   }

}

我们有一个表示配置的POCO对象：

And we have a POCO object representing the configuration:

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

现在我们在 Startup.cs中构建配置：

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();
    }
}

请注意， appsettings.json 将在.NET Core 2.0中默认注册。如果需要，我们还可以注册 appsettings。{Environment} .json 每个环境的配置文件。

Note that appsettings.json will be registered by default in .NET Core 2.0. We can also register an appsettings.{Environment}.json config file per environment if needed.

如果需要要将配置注入到控制器中，我们需要在运行时注册它。我们通过 Startup.ConfigureServices ：

If we want to inject our configuration to our controllers, we'll need to register it with the runtime. We do so via Startup.ConfigureServices:

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.GetSection("MyConfig"));
}

我们像这样注入它：

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);
}

完整的启动类：

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.GetSection("MyConfig"));
    }
}

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