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)
{ /* ... */ }
"Cocoar" and related marks are trademarks of COCOAR e.U. Use of the name in forks or derivatives should preserve attribution and avoid implying official endorsement. See TRADEMARKS for permitted and restricted uses.
