dotnet appsettings reload

using System.Text.Json;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Options;

var builder = WebApplication.CreateBuilder(args);

// i'm here only for demo purposes to create separate file, it might be something like appsettings.foo.json instead
File.WriteAllText("demo.json", JsonSerializer.Serialize(new { demo = new Demo { Number = 42 } }));

// add one more configuration file side by side with appsettings.json
builder.Configuration.AddJsonFile("demo.json", optional: true, reloadOnChange: true);

// how we are usualy registering settings
builder.Services.AddSingleton<Demo>(p => p.GetRequiredService<IConfiguration>().GetSection(nameof(Demo)).Get<Demo>());

// alternative approach, it can live side by side with previous one, it does not registers `Demo` but instead adds IOptions, IOptionsSnapshot and IOptionsMonitor
builder.Services.Configure<Demo>(builder.Configuration.GetSection(nameof(Demo)));


var app = builder.Build();

app.MapGet("/", () => "Hello World!");

// how we are usualy working with configs
// i wont be refreshed
app.MapGet("/singleton", ([FromServices]Demo demo) => demo);
// curl localhost:5000/singleton
// {"number":42}

// alternative approach with IOptions
// technicaly works same way as previous and wont be refreshed
app.MapGet("/options", ([FromServices]IOptions<Demo> demo) => demo.Value);
// curl localhost:5000/options
// {"number":42}

// alternative approach with IOptionsSnapshot
// i will be refreshed, BUT i will add some perf because computing on each request
app.MapGet("/snapshot", ([FromServices]IOptionsSnapshot<Demo> demo) => demo.Value);
// curl localhost:5000/snapshot
// {"number":42}

// alternative approach with IOptionsSnapshot
// i will be refreshed
app.MapGet("/monitor", ([FromServices]IOptionsMonitor<Demo> demo) => demo.CurrentValue);
// curl localhost:5000/monitor
// {"number":42}

app.Run();

/*

curl -s localhost:5000/singleton | jq
curl -s localhost:5000/options | jq
curl -s localhost:5000/snapshot | jq
curl -s localhost:5000/monitor | jq

echo -n '{"demo":{"Number":5}}' > demo.json

# last two will be updated
# https://learn.microsoft.com/en-us/aspnet/core/fundamentals/configuration/options
*/

public class Demo {
    public int Number { get; set; }
}