출처 : https://stackoverflow.com/questions/34884854/convert-listint-to-byte
List -> byte[]
byte[] bytes = lista .SelectMany(x => x) .SelectMany(BitConverter.GetBytes) .ToArray();
byte[] -> List
List<int> list = bytes
.Select((item, index) => new {item, index})
.GroupBy(x => x.index/4)
.Select(g => g.Select(x => x.item).ToArray())
.Select(x => BitConverter.ToInt32(x, 0)) .ToList();