https://blog.csdn.net/zhangxiao0122/article/details/88570472

根据论坛及博客整理。

原有list集合，

2. List<CommodityInfo> commodityInfoList = new List<CommodityInfo>();

3. public class CommodityInfo

4. {

5. public string StoreID {get; set;}

6. public string CommodityID {get; set;}

7. public string CommodityName {get; set;}

8. public decimal CommodityPrice {get; set;}

9. }

如何按照StoreID进行分组，形成如下List

1. List<StoreInfo> storeInfoList = new List<StoreInfo>();

3. public class StoreInfo

4. {

5. public string StoreID {get; set;}

6. public List<CommodityInfo> List {get; set;}

7. }

方案为：

1. //根据 StoreID分组

2. storeInfoList = commodityInfoList.GroupBy(x =>x.StoreID)

3. .Select(group => new StoreInfo

4. {

5. StoreID= group.Key,

6. List= group.ToList()

7. }).ToList();

GroupBy  添加分组条件，多个条件时用逗号“，”隔开

　　.GroupBy(x => new {x.CommodityID, x.CommodityName, x.StoreID})

Select 用于分组之后输出的结果集，可以new 出一个实体，或者直接new 个对象