[c#] Getting value from appsettings.json in .net core

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"
    }
}

Startup:

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"));
    }
}

Model:

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

Controller:

public class HomeController : Controller
{
    private readonly AppSettings _mySettings;

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

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

.NET core 3.X

no need to create new model and to set in Startup.cs.

Controller Add new package - using 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() };
    }
}

For ASP.NET Core 3.1 you can follow this guide:

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

When you create a new ASP.NET Core 3.1 project you will have the following configuration line in Program.cs:

Host.CreateDefaultBuilder(args)

This enables the following:

1. 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.
2. appsettings.json using the JSON configuration provider.
3. appsettings.Environment.json using the JSON configuration provider. For example, appsettings.Production.json and appsettings.Development.json.
4. App secrets when the app runs in the Development environment.
5. Environment variables using the Environment Variables configuration provider.
6. Command-line arguments using the Command-line configuration provider.

This means you can inject IConfiguration and fetch values with a string key, even nested values. Like IConfiguration["Parent:Child"];

Example:

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();
    }
}

I think the best option is:

1. Create a model class as config schema

2. Register in DI: services.Configure(Configuration.GetSection("democonfig"));

3. Get the values as model object from DI in your controller:

   private readonly your_model myConfig;
   public DemoController(IOptions<your_model> configOps)
   {
       this.myConfig = configOps.Value;
   }
   

From Asp.net core 2.2 to above you can code as below:

Step 1. Create an AppSettings class file.

This file contains some methods to help get value by key from the appsettings.json file. Look like as code below:

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>();
      }
  }
}

Step 2. Initial configuration for AppSettings object

We need to declare and load appsettings.json file when the application starts, and load configuration information for AppSettings object. We will do this work in the constructor of the Startup.cs file. Please notice line AppSettings.Instance.SetConfiguration(Configuration);

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);       
}

Okay, now I have an appsettings.json file with some keys as below:

{
  "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": "[email protected]",
      "Pass": "123456"
    }
  }
}

Step 3. Read config value from an action

I make demo an action in Home controller as below :

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);
    }
}

And below is the result:

Click to see result

For more information, you can refer article get value from appsettings.json in asp.net core for more detail code.

In my case it was simple as using the Bind() method on the Configuration object. And then add the object as singleton in the DI.

var instructionSettings = new InstructionSettings();
Configuration.Bind("InstructionSettings", instructionSettings);
services.AddSingleton(typeof(IInstructionSettings), (serviceProvider) => instructionSettings);

The Instruction object can be as complex as you want.

{  
 "InstructionSettings": {
    "Header": "uat_TEST",
    "SVSCode": "FICA",
    "CallBackUrl": "https://UATEnviro.companyName.co.za/suite/webapi/receiveCallback",
    "Username": "s_integrat",
    "Password": "X@nkmail6",
    "Defaults": {
    "Language": "ENG",
    "ContactDetails":{
       "StreetNumber": "9",
       "StreetName": "Nano Drive",
       "City": "Johannesburg",
       "Suburb": "Sandton",
       "Province": "Gauteng",
       "PostCode": "2196",
       "Email": "[email protected]",
       "CellNumber": "0833 468 378",
       "HomeNumber": "0833 468 378",
      }
      "CountryOfBirth": "710"
    }
  }

This tends to happen particularly with vscode as I'd assume because of how one configures the launch.json.

Based on this answer I had to reconfigure the base path the configuration is being searched for to that of DLL's path, and since the default setting was optional it was hard to track this down on a .net core 3.1 & net 5.0 app. Here's how I've reconfigured

Program.cs:

using System;
using System.IO;
using System.Reflection;
using Microsoft.Extensions.Configuration;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Hosting;

namespace API
{
    public class Program
    {
        public static int Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
            return 0;
        }

        public static IHostBuilder CreateHostBuilder(string[] args)
        {
            return Host.CreateDefaultBuilder(args)
            .ConfigureAppConfiguration(c =>
            {
                var codeBase = Assembly.GetExecutingAssembly().Location;
                var uri = new UriBuilder(codeBase);
                var path = Uri.UnescapeDataString(uri.Path);
                var assembyDirectory = Path.GetDirectoryName(path);
                c.SetBasePath(assembyDirectory);
            })
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            })
            ;
        }
    }
}

I could access the configuration fine in Startup.cs:

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Model;

namespace API
{
    public class Startup
    {
        public IConfiguration Configuration { get; }

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

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            var myOptions = Configuration.To<ApiConfig>();
            services.AddAuthentication(myOptions.Secret);
            services.AddControllers();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.UseRouting();
            app.UseAuthentication();
            app.UseAuthorization();
            app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
        }
    }
}

In the constructor of Startup class, you can access appsettings.json and many other settings using the injected IConfiguration object:

Startup.cs Constructor

    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;

        //here you go
        var myvalue = Configuration["Grandfather:Father:Child"];

    }

public IConfiguration Configuration { get; }

Contents of appsettings.json

  {
  "Grandfather": {
    "Father": {
      "Child": "myvalue"
    }
  }

Its simple: In appsettings.json

  "MyValues": {
    "Value1": "Xyz"
  }

In .cs file:

static IConfiguration conf = (new ConfigurationBuilder().SetBasePath(Directory.GetCurrentDirectory()).AddJsonFile("appsettings.json").Build());
        public static string myValue1= conf["MyValues:Value1"].ToString();

Just create An AnyName.cs file and paste following code.

using System;
using System.IO;
using Microsoft.Extensions.Configuration;

namespace Custom
{
    static class ConfigurationManager
    {
        public static IConfiguration AppSetting { get; }
        static ConfigurationManager()
        {
            AppSetting = new ConfigurationBuilder()
                    .SetBasePath(Directory.GetCurrentDirectory())
                    .AddJsonFile("YouAppSettingFile.json")
                    .Build();
        }
    }
}

Must replace YouAppSettingFile.json file name with your file name.
Your .json file should look like below.

{
    "GrandParent_Key" : {
        "Parent_Key" : {
            "Child_Key" : "value1"
        }
    },
    "Parent_Key" : {
        "Child_Key" : "value2"
    },
    "Child_Key" : "value3"
}

Now you can use it.
Don't forget to Add Reference in your class where you want to use.

using Custom;

Code to retrieve value.

string value1 = ConfigurationManager.AppSetting["GrandParent_Key:Parent_Key:Child_Key"];
string value2 = ConfigurationManager.AppSetting["Parent_Key:Child_Key"];
string value3 = ConfigurationManager.AppSetting["Child_Key"];

Adding to David Liang's answer for Core 2.0 -

appsettings.json file's are linked to ASPNETCORE_ENVIRONMENT variable.

ASPNETCORE_ENVIRONMENT can be set to any value, but three values are supported by the framework: Development, Staging, and Production. If ASPNETCORE_ENVIRONMENT isn't set, it will default to Production.

For these three values these appsettings.ASPNETCORE_ENVIRONMENT.json files are supported out of the box - appsettings.Staging.json, appsettings.Development.json and appsettings.Production.json

The above three application setting json files can be used to configure multiple environments.

Example - appsettings.Staging.json

{
    "Logging": {
        "IncludeScopes": false,
        "LogLevel": {
            "System": "Information",
            "Microsoft": "Information"
        }
    },
    "MyConfig": "My Config Value for staging."
}

Use Configuration["config_var"] to retrieve any configuration value.

public class Startup
{
    public Startup(IHostingEnvironment env, IConfiguration config)
    {
        Environment = env;
        Configuration = config;
        var myconfig = Configuration["MyConfig"];
    }

    public IConfiguration Configuration { get; }
    public IHostingEnvironment Environment { get; }
}

1. Add the required key here like this. In this case its SecureCookies:

2. In startup.cs, add the constructor

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

3. Access the settings using Configuration["SecureCookies"]

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

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

    }

I guess the simplest way is by DI. An example of reaching into Controller.

// StartUp.cs
public void ConfigureServices(IServiceCollection services)
{
    ...
    // for get appsettings from anywhere
    services.AddSingleton(Configuration);
}

public class ContactUsController : Controller
{
    readonly IConfiguration _configuration;

    public ContactUsController(
        IConfiguration configuration)
    {
        _configuration = configuration;

        // sample:
        var apiKey = _configuration.GetValue<string>("SendGrid:CAAO");
        ...
    }
}