private int GetListIndex(BufferCacheKey key)
 {
     lock (this.state)
         return(this.parentMap.GetOrAdd(key, this.parentMap.Count + 1));
 }
        public int GetListIndex(IReference reference)
        {
            BufferCacheKey cacheKey = new BufferCacheKey(this.GetParentKeyType(reference));

            return(this.GetListIndex(cacheKey));
        }