Read appsettings.json file in ASP.NET Core .NET 8

In ASP.NET Core .NET 8, you can read configuration settings from the appsettings.json file using the built-in configuration system/manager. 

Please follow the below steps to create the project.

• Create the ASP.NET Core Web API via Visual Studio 2022
• Check appsettings.json file is present if not add the file.

Appsettings.json file

Your appsettings.json file in your project looks like below. 

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  }  
  "AllowedHosts": "*"
}

Please add the below sample setting to your appsettings.json file,

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "MySettings": {
    "Url": "https://techiehook.com",
    "UserName": "techihook",
    "Password": "pass1234",
    "SerialNumber": "123-456-789-123"
  },
  "AllowedHosts": "*"
}

Bind configuration to a class:

We will create a class that matches the structure of your settings in appsettings.json. For example:

namespace AppSettingExample
{
    public class MyAppSettings
    {
        public string Url { get; set; }
        public string UserName { get; set; }
        public string Password { get; set; }
        public string SerialNumber { get; set; }
    }
}

Register the class:

We will register the MyAppSettings class with the dependency injection container in Program.cs.

using AppSettingExample;
using System.Runtime;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

// Add this line to your program.cs
builder.Services.Configure<MyAppSettings>(builder.Configuration.GetSection("MySettings"));

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

Inject and use the settings in a controller:

We will create a controller called SettingsController.cs and add the Get() method to read the settings from the appsettings.json file as shown below,

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Options;
using System.Runtime;

namespace AppSettingExample.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class SettingsController : ControllerBase
    {
        private readonly MyAppSettings _mySettings;

        public SettingsController(IOptions<MyAppSettings> mySettings)
        {
            _mySettings = mySettings.Value;
        }

        [HttpGet(Name = "GetSettings")]
        public IActionResult Get()
        {
            return Ok(_mySettings);
        }
    }
}

Run the application and see the output:

When we run the application, the application reads the configuration settings in appsettings.json file and map the each value in the MyAppSettings class and display it as shown below,