C#List<long>与String（Linq）

1、string => List<long>

string ShopIds = "1,2,3";

var ShopIdList = ShopIds.Split(',').Select(p => p.ToLong()).ToList()

2、List<long> => string

List<long> = new List<long>{1,2,3};

string ShopIds = string.Join(",", shopSkuIds);