I have this interface for a C# class. ``` public interface IPriorityQueue<TItem, TPriority> : IEnumerable<TItem> { void Enqueue(TItem node, TPriority priority); TItem Dequeue(); void Clear(); bool Contains(TItem node); void Remove(TItem node); void UpdatePriority(TItem node, TPriority priority); TItem First { get; } int Count { get; } } ``` Show me how to get the length of the priority queue?