Extension method for cutting an enumerable into batches

EnumerableExtensions.cs

public static class EnumerableExtensions
    {
        public static IEnumerable<IEnumerable<T>> Batches<T>(this IEnumerable<T> items, int batchSize)
        {
            if (batchSize <= 0)
            {
                throw new ArgumentException("Batch size must be greater than 0");
            }

            var itemsList = items as IList<T> ?? items.ToList();
            var itemCount = itemsList.Count;
            var numBatches = Math.Ceiling((decimal) itemCount / batchSize);

            for (int i = 0; i < numBatches; i++)
            {
                yield return itemsList.Skip(i * batchSize).Take(batchSize);
            }
        }
    }