Demonstrates the using syntax of AsyncSemaphore.

ThreadSafeDictionaryWithAsyncSemaphore.cs

using Microsoft.VisualStudio.Threading; // From the Microsoft.VisualStudio.Threading NuGet package

public class ThreadSafeDictionary<K, V>
{
  private readonly AsyncSemaphore semaphore = new AsyncSemaphore(1);
  private readonly Dictionary<K, V> inner = new Dictionary<K, V>();

  public async Task AddThenRemoveAsync(K key, V value, CancellationToken cancellationToken = default(CancellationToken)) {
    using (await this.semaphore.EnterAsync(cancellationToken)) {
      this.inner.Add(key, value);
      await Task.Delay(50); // still holding semaphore, so no one can get it!
      this.inner.Remove(key);
    }
  }
}