✅ How to edit and save specific appsettings.json (project root) section?

   
public void SetYear(int year)
        {
            var config = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .AddEnvironmentVariables()
                .Build()
                .Get<Config>();

            config.ConfigurableYear = year;

            var jsonWriteOptions = new JsonSerializerOptions()
            {
                WriteIndented = true,
                
            };

            var newJson = JsonSerializer.Serialize(config, jsonWriteOptions);

            var appSettingsPath = Path.Combine(Directory.GetCurrentDirectory(), "appsettings.json");
            File.WriteAllText(appSettingsPath, newJson);
            
        }

   public class ConfigService : IConfigService
    {
        private readonly Configs _configs;

        public ConfigService(IOptions<Configs> configs)
        {
            _configs = configs.Value;
        }

        public void SetYear(int year)
        {

            _configs.ConfigurableYear = year;          
        }
}

            services.Configure<Configs>(options => Configuration.GetSection("ConfigurableYear").Bind(options));

{
  "My": {
    "Foo": {
      "Kix": 5
    }
  }
}

public class FooOptions
{
  public const string SectionName = "My:Foo";

  public string Bar {get;set;} = "default value for bar";
  public int Kix {get;set;} = -1;
  public DateTime? Pouet {get;set;} = default;
}

namespace Microsoft.Extensions.DependencyInjection; // <==== recommanded for service.Add so that you don't clutter Startup file

public class FooServiceCollectionExtensions
{
  public static IServiceCollection AddFoo(this IServiceCollection services) =>
    services
      .AddOptions<FooOptions>()
      .BindConfiguration(FooOptions.SectionName)
      .Validate(options => options.Kix >= 0, $"The configuration key '{FooOptions.SectionName}:{nameof(Kix)}' cannot be negative")
      ;

  public static IServiceCollection AddFoo(this IServiceCollection services, Action<FooOptions> configure) =>
    services
      .AddFoo()
      .Configure(configure);

services.AddFoo();
// or
services.AddFoo(fooOptions => fooOptions.Kix = 12);

public class Bar
{
  private readonly FooOptions _fooOptions;

  // .Value in ctor is fine only if it's always ever a non-changing value (no reload and/or no scoped resolution)
  public Bar(IOptions<FooOptions> fooOptions)
    => _fooOptions = fooOptions.Value;
}

Azure App Configuration provides a service to centrally manage application settings and feature flags. Modern programs, especially programs running in a cloud, generally have many components that are distributed in nature. Spreading configuration settings across these components can lead to hard-to-troubleshoot errors during an application deployment. Use App Configuration to store all the settings for your application and secure their accesses in one place.