SemaphoreSlimExtensions

SemaphoreSlimExtensions.cs

public static class SemaphoreSlimExtensions
{
    /// <summary>
    /// Blocks the current thread until it can enter the <see cref="SemaphoreSlim"/>. Returns an <see cref="IDisposable"/> to be used in <c>using</c>.
    /// </summary>
    /// <param name="semaphore">A <see cref="SemaphoreSlim"/> to lock.</param>
    /// <returns>An <see cref="IDisposable"/> that will release the <see cref="SemaphoreSlim"/> when disposed.</returns>
    public static IDisposable Lock(this SemaphoreSlim semaphore)
    {
        semaphore.Wait();
        return new SemaphoreReleaser(semaphore);
    }

    /// <summary>
    /// Asynchronously waits to enter the <see cref="SemaphoreSlim"/>, while observing a
    /// <see cref="CancellationToken"/>. Returned task resolves an <see cref="IDisposable"/> to be used in <c>using</c>.
    /// </summary>
    /// <returns>
    /// A task that will complete when the semaphore has been entered.
    /// Task contains An <see cref="IDisposable"/> that will release the <see cref="SemaphoreSlim"/> when disposed.
    /// </returns>
    /// <param name="semaphore">A <see cref="SemaphoreSlim"/> to lock.</param>
    /// <param name="cancellationToken">
    /// The <see cref="CancellationToken"/> token to observe.
    /// </param>
    public static async Task<IDisposable> LockAsync(this SemaphoreSlim semaphore, CancellationToken cancellationToken = default)
    {
        var task = semaphore.WaitAsync(cancellationToken);
        await task.ConfigureAwait(false);
        return task.Status == TaskStatus.RanToCompletion ? new SemaphoreReleaser(semaphore) : new DisposableNoOp();
    }

    private sealed class SemaphoreReleaser(SemaphoreSlim semaphore) : IDisposable
    {
        private bool released;

        public void Dispose()
        {
            if (released) return;
            semaphore.Release();
            this.released = true;
        }
    }

    private sealed class DisposableNoOp : IDisposable
    {
        public void Dispose()
        {
        }
    }
}