C# 将数组转换成字符串

List<OrderEntity> list = new List<OrderEntity>(){ new OrderEntity(){ Id=1001, Line=1 ,Item="TEST1"}, new OrderEntity(){ Id=1002, Line=2 ,Item="TEST2"}, new OrderEntity(){ Id=1003, Line=3 ,Item="TEST3"}};var array = list.Select(t => t.Id).ToArray();var ids = string.Join(",", array);