public long Count(IQueryOptions <TEntity> queryOptions)
        {
            var query = new Query(_kind)
            {
                Projection = { "__key__" }
            };

            if (queryOptions != null)
            {
                var options = queryOptions.GetOptions();

                query = new Query(_kind)
                {
                    Filter     = queryOptions.GetFilter(),
                    Projection = { "__key__" },
                    Order      = { options.PropertyOrders },
                    Limit      = options.Limit
                };
            }

            var results = _database.RunQuery(query);

            return(results.Entities.Count);
        }