public static void GetSection()
    {
        Configuration = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json")
            .Build();

        string BConfig = Configuration.GetSection("ConnectionStrings")["BConnection"];

    }

. net core 3。X

不需要创建新的模型并在Startup.cs中设置。

控制器 添加新包-使用Microsoft.Extensions.Configuration;

public class HomeController : Controller
{
    private readonly IConfiguration _mySettings;

    public HomeController (IConfiguration mySettings)
    {
         _mySettings= mySettings;
    }
 
    //ex: you can get value on below function 
    public IEnumerable<string> Get()
    {
        var result = _config.GetValue<string>("AppSettings:Version"); // "One"
        return new string[] { result.ToString() };
    }
}

我只是创建了一个静态类，并在Startup.cs中设置了一个配置变量

public static class GlobalConfig { 
    public static IConfiguration config { get; set; } 
}

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        GlobalConfig.config = configuration;

    }
}

然后在任何地方使用它:

var keyVal = GlobalConfig.config["key"];

似乎是访问配置文件并使其在任何地方可用的最简单的方法。

从Asp.net core 2.2到以上版本，你可以编写如下代码:

步骤1。创建一个AppSettings类文件。

这个文件包含一些帮助从appsettings中按键获取值的方法。json文件。如下代码所示:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace ReadConfig.Bsl
{
  public class AppSettings
  {
      private static AppSettings _instance;
      private static readonly object ObjLocked = new object();
      private IConfiguration _configuration;

      protected AppSettings()
      {
      }

      public void SetConfiguration(IConfiguration configuration)
      {
          _configuration = configuration;
      }

      public static AppSettings Instance
      {
          get
          {
              if (null == _instance)
              {
                  lock (ObjLocked)
                  {
                      if (null == _instance)
                          _instance = new AppSettings();
                  }
              }
              return _instance;
          }
      }

      public string GetConnection(string key, string defaultValue = "")
      {
          try
          {
              return _configuration.GetConnectionString(key);
          }
          catch
          {
              return defaultValue;
          }
      }

      public T Get<T>(string key = null)
      {
          if (string.IsNullOrWhiteSpace(key))
              return _configuration.Get<T>();
          else
              return _configuration.GetSection(key).Get<T>();
      }

      public T Get<T>(string key, T defaultValue)
      {
          if (_configuration.GetSection(key) == null)
              return defaultValue;

          if (string.IsNullOrWhiteSpace(key))
              return _configuration.Get<T>();
          else
              return _configuration.GetSection(key).Get<T>();
      }

      public static T GetObject<T>(string key = null)
      {
          if (string.IsNullOrWhiteSpace(key))
              return Instance._configuration.Get<T>();
          else
          {
              var section = Instance._configuration.GetSection(key);
              return section.Get<T>();
          }
      }

      public static T GetObject<T>(string key, T defaultValue)
      {
          if (Instance._configuration.GetSection(key) == null)
              return defaultValue;

          if (string.IsNullOrWhiteSpace(key))
              return Instance._configuration.Get<T>();
          else
              return Instance._configuration.GetSection(key).Get<T>();
      }
  }
}

步骤2。AppSettings对象的初始配置

我们需要声明和加载appsettings。json文件，加载AppSettings对象的配置信息。我们将在Startup.cs文件的构造函数中完成这项工作。 请注意行AppSettings.Instance.SetConfiguration(配置);

public Startup(IHostingEnvironment evm)
{
    var builder = new ConfigurationBuilder()
      .SetBasePath(evm.ContentRootPath)
      .AddJsonFile("appsettings.json", true, true)
      .AddJsonFile($"appsettings.{evm.EnvironmentName}.json", true)
      .AddEnvironmentVariables();
    Configuration = builder.Build(); // load all file config to Configuration property 
    AppSettings.Instance.SetConfiguration(Configuration);       
}

现在我有了appsettings。Json文件与一些关键字如下:

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "ConnectionString": "Data Source=localhost;Initial Catalog=ReadConfig;Persist Security Info=True;User ID=sa;Password=12345;"
  },
  "MailConfig": {
    "Servers": {
      "MailGun": {
        "Pass": "65-1B-C9-B9-27-00",
        "Port": "587",
        "Host": "smtp.gmail.com"
      }
    },
    "Sender": {
      "Email": "example@gmail.com",
      "Pass": "123456"
    }
  }
}

步骤3。从操作中读取配置值

我在Home控制器中演示一个动作，如下所示:

public class HomeController : Controller
{
    public IActionResult Index()
    {
        var connectionString = AppSettings.Instance.GetConnection("ConnectionString");
        var emailSender = AppSettings.Instance.Get<string>("MailConfig:Sender:Email");
        var emailHost = AppSettings.Instance.Get<string>("MailConfig:Servers:MailGun:Host");

        string returnText = " 1. Connection String \n";
        returnText += "  " +connectionString;
        returnText += "\n 2. Email info";
        returnText += "\n Sender : " + emailSender;
        returnText += "\n Host : " + emailHost;

        return Content(returnText);
    }
}

结果如下:

点击查看结果

ASP。NET Core 3.1你可以遵循以下指南:

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-3.1

当您创建一个新的ASP。在Program.cs中，你会有如下的配置行:

Host.CreateDefaultBuilder(args)

这将启用以下功能:

ChainedConfigurationProvider : Adds an existing IConfiguration as a source. In the default configuration case, adds the host configuration and setting it as the first source for the app configuration. appsettings.json using the JSON configuration provider. appsettings.Environment.json using the JSON configuration provider. For example, appsettings.Production.json and appsettings.Development.json. App secrets when the app runs in the Development environment. Environment variables using the Environment Variables configuration provider. Command-line arguments using the Command-line configuration provider.

这意味着您可以注入IConfiguration并使用字符串键获取值，甚至是嵌套值。像IConfiguration“父母:孩子”;

例子:

appsettings.json

{
  "ApplicationInsights":
    {
        "Instrumentationkey":"putrealikeyhere"
    }
}

WeatherForecast.cs

[ApiController]
[Route("[controller]")]
public class WeatherForecastController : ControllerBase
{
    private static readonly string[] Summaries = new[]
    {
        "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
    };

    private readonly ILogger<WeatherForecastController> _logger;
    private readonly IConfiguration _configuration;

    public WeatherForecastController(ILogger<WeatherForecastController> logger, IConfiguration configuration)
    {
        _logger = logger;
        _configuration = configuration;
    }

    [HttpGet]
    public IEnumerable<WeatherForecast> Get()
    {
        var key = _configuration["ApplicationInsights:InstrumentationKey"];

        var rng = new Random();
        return Enumerable.Range(1, 5).Select(index => new WeatherForecast
        {
            Date = DateTime.Now.AddDays(index),
            TemperatureC = rng.Next(-20, 55),
            Summary = Summaries[rng.Next(Summaries.Length)]
        })
        .ToArray();
    }
}

    public static void GetSection()
    {
        Configuration = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json")
            .Build();

        string BConfig = Configuration.GetSection("ConnectionStrings")["BConnection"];

    }