Илья Глебов

class CustomDependencyManager {
  class CustomDependency : CacheDependency {
    public void Invalidate() {
      NotifyDependencyChanged(this, EventArgs.Empty);
     }
  }
  public static CustomDependencyManager Instance = new CustomDependencyManager();

  private readonly ConcurrentDictionary<string, CustomDependency> dependencies = new ConcurrentDictionary<string, CustomDependency>();

  private CustomDependency GetCacheDependencyInternal(string xxx) {
    return dependencies.GetOrAdd(xxx, s => new CustomDependency());
  }

  public void Invalidate(string xxx) {
    GetCacheDependencyInternal(xxx).Invalidate();
  }
  
  public CacheDependency For(string xxx) {
    GetCacheDependencyInternal(xxx);            
  }
}

Cache.Insert("prefix_"+xxx+"_"+yyyy, data, CustomDependencyManager.Instance.For(xxx), DateTime.Now.AddSeconds(1), Cache.NoSlidingExpiration, CacheItemPriority.High, null);

...
...
// Пора сбросить кеш 
CustomDependencyManager.Instance.Invalidate(xxx);