Program.cs

using System.Text.Json.Serialization;
using Configuration.Writable;
using Configuration.Writable.FormatProvider;
using Example.WebApi;
using Microsoft.AspNetCore.Http.HttpResults;
using Microsoft.AspNetCore.Mvc;
using NSwag.AspNetCore;

var builder = WebApplication.CreateSlimBuilder(args);

// Configuration.Writable
builder.Services.AddWritableOptions(services =>
{
    // shared configuration for all options types
    services.FormatProvider = new JsonAotFormatProvider(SampleSettingSerializerContext.Default);

    // if you want to standard system configuration location, use services.UseStandardSaveDirectory("your-app-id");
    // e.g. %APPDATA%\your-app-id\appdata-setting.json on Windows
    // services.UseStandardSaveDirectory("your-app-id");

    // add SampleSetting
    services.Add<SampleSetting>(c =>
    {
        c.UseFile("appsettings.json");
        c.SectionName = "MySetting";
        c.WithValidator<SampleSettingValidator>();
    });
});

// default Configuration
builder.Services.ConfigureHttpJsonOptions(options =>
{
    options.SerializerOptions.TypeInfoResolverChain.Insert(
        0,
        SampleSettingSerializerContext.Default
    );
});
builder.Services.AddOpenApiDocument();

var app = builder.Build();
app.UseOpenApi();
app.UseSwaggerUi(options =>
{
    options.Path = "";
});

var configApi = app.MapGroup("/config");
configApi.MapGet(
    "/get",
    (IReadOnlyOptions<SampleSetting> options) =>
    {
        var settings = options.CurrentValue;
        return settings;
    }
);

configApi.MapGet(
    "/set/{name}",
    async ([FromServices] IWritableOptions<SampleSetting> options, string name) =>
    {
        try
        {
            await options.SaveAsync(setting => setting.Name = name);
            return Results.Ok();
        }
        catch (Exception ex)
        {
            return Results.Text(content: ex.Message, statusCode: 500);
        }
    }
);

app.Run();