Soenneker.Utils.SingletonDictionary 4.0.1119

Soenneker.Utils.SingletonDictionary

A flexible singleton dictionary with double-check async locking, sync/async disposal, and external initialization

Features

• ✅ Async and sync initialization patterns
• ✅ Optional cancellation support
• ✅ Async and sync access methods
• ✅ Fully disposable (sync and async)
• ✅ Thread-safe with AsyncLock from Nito.AsyncEx

Installation

dotnet add package Soenneker.Utils.SingletonDictionary

✨ Example Usage

Here’s an example using SingletonDictionary to manage singleton HttpClient instances keyed by configuration (e.g. timeout):

public class HttpRequester : IDisposable, IAsyncDisposable
{
    private readonly SingletonDictionary<HttpClient> _clients;

    public HttpRequester()
    {
        _clients = new SingletonDictionary<HttpClient>((args) =>
        {
            var socketsHandler = new SocketsHttpHandler
            {
                PooledConnectionLifetime = TimeSpan.FromMinutes(10),
                MaxConnectionsPerServer = 10
            };

            var client = new HttpClient(socketsHandler)
            {
                Timeout = TimeSpan.FromSeconds((int)args[0])
            };

            return client;
        });
    }

    public async ValueTask Get()
    {
        var client = await _clients.Get("100", 100);
        await client.GetAsync("https://google.com");
    }

    public async ValueTask DisposeAsync()
    {
        GC.SuppressFinalize(this);
        await _clients.DisposeAsync();
    }

    public void Dispose()
    {
        GC.SuppressFinalize(this);
        _clients.Dispose();
    }
}

🔍 Internals

SingletonDictionary<T> is backed by a ConcurrentDictionary<string, T> and supports:

• Multiple constructor overloads for async/sync factory functions
• Internal double-checked locking on access
• Deferred/lazy factory execution
• Proper disposal of values (both sync and async interfaces)
• Safe mutation via SetInitialization before first use

Example constructor overloads include:

new SingletonDictionary<T>(Func<string, object[], ValueTask<T>> factory);
new SingletonDictionary<T>(Func<object[], T> factory);
new SingletonDictionary<T>(Func<string, CancellationToken, object[], ValueTask<T>> factory);
// And more...

You can also initialize manually:

var dict = new SingletonDictionary<MyService>();
dict.SetInitialization((args) => new MyService(args));

🛡️ Thread Safety

This library uses AsyncLock for safe concurrent access in async contexts, and synchronously via Lock() for blocking methods. This avoids race conditions and guarantees safe singleton creation.