internal Enumerator(BandCollection <T> bandCollection)
            {
                this = default(BandCollection <T> .Enumerator);

                collection = bandCollection;
                ver        = bandCollection.version;
            }
            public bool MoveNext()
            {
                BandCollection <T> list = collection;

                if (next < list.Count && ver == list.version)
                {
                    current = list [next++];
                    return(true);
                }
                if (ver != collection.version)
                {
                    throw new InvalidOperationException("Collection was modified; enumeration operation may not execute.");
                }
                next = -1;
                return(false);
            }