var builder = WebApplication.CreateBuilder(args);
// Register layered configuration (file + environment overlay)
builder.Services.AddCocoarConfiguration([
Rule.From.File("appsettings.json").Select("App").For<AppSettings>(),
Rule.From.Environment("APP_").For<AppSettings>()
]);
var app = builder.Build();
// Simple endpoint: inject concrete snapshot (Scoped)
app.MapGet("/feature", (AppSettings cfg) => new {
snapshotFlag = cfg.FeatureFlag, // Value at scope start (request)
message = cfg.Message
});
// Reactive usage example (background logging)
var reactive = app.Services.GetRequiredService<IReactiveConfig<AppSettings>>();
var _ = reactive.Subscribe(c => Console.WriteLine($"[Config Updated] FeatureFlag={c.FeatureFlag}"));
app.Run();
public sealed class AppSettings
{
public bool FeatureFlag { get; set; }
public string Message { get; set; } = string.Empty;
}
appsettings.json changed? — future requests see the updated snapshot; reactive stream subscribers get a push..
Reactive by Default
Every configuration type you map gets a free reactive companion:
You Have
You Also Automatically Have
AppSettings
IReactiveConfig<AppSettings>
IReactiveConfig<T> gives you:
CurrentValue – latest stable value
Subscribe(...) – push updates only when actual content changes
Safe & error-resilient stream: subscriber exceptions are logged, never terminate the pipeline
Guidance:
In request/short-lived scopes: inject the concrete type (AppSettings) for a consistent snapshot
In background services / singletons: inject IReactiveConfig<T>
Need a frozen value inside a singleton? Capture live.CurrentValue once (rarely required)
Rule Basics
A rule = provider + (optional selection/query) + target config type.
Order matters: later rules overwrite earlier values per flattened key (deterministic last-write-wins).
var rules = new [] {
Rule.From.File("appsettings.json").For<AppSettings>(),
Rule.From.Environment("APP_").For<AppSettings>()
};
Additional options (add only when needed):
Rule.From.File("secrets.json")
.Select("Secrets:Db") // select subtree
.Mount("Database") // mount under a new path
.Required() // fail the rule if source missing
.For<DatabaseConfig>();
Interface Binding (Optional)
Start without it. Add when you want to inject contracts instead of concretes.
services.AddCocoarConfiguration(rules, [
Bind.Type<AppSettings>().To<IAppSettings>()
]);
public sealed class Handler(IAppSettings cfg, IReactiveConfig<IAppSettings> live)
{ /* ... */ }
