List分组和排序

Posted 2020-10-12 杜子烟

 1 //分组
 2 var ll= lst.GroupBy(x => new { x.Id, x.Name }).Select(x => new
 3             {
 4                 Key = x.Key,
 5                 Id = x.First().Id,
 6                 Name = x.First().Name,
 7                 Count = x.Sum(s => s.Value)
 8             });
 9 
10 
11 //排序
12 List<int> list = new List<int>(); 
13 list.Sort();// 升序排序 
14 list.Reverse();// 反转顺序
15 
16 List<int> list= new List<int>(){5,1,22,11,4}; 
17 list.Sort((x, y) => x.CompareTo(y));//升序 
18 list.Sort((x, y) => -x.CompareTo(y));//降序
19 
20 //定义一个集合
21 var list = new List<Object>();//这里的Type为对象类型
22 //假设list已经有数据存进去，根据对象的某个字段升序或降序
23 var orderInfo = list.OrderByDescending(a => a.ProductID).ToList();//降序
24 var orderInfo = list.OrderBy(a => a.ProductID).ToList();//升序