【EFCORE笔记】联接运算与数据分组

Join Operations

Method Name	Description	More Information
Join	Joins two sequences based on key selector functions and extracts pairs of values.	Enumerable.Join Queryable.Join
GroupJoin	Joins two sequences based on key selector functions and groups the resulting matches for each element.	Enumerable.GroupJo in Queryable.GroupJoin

Grouping Data

Method Name	Description	More Information
GroupBy	Groups elements that share a common attribute. Each group is represented by an IGrouping<TKey,TElement> object.	Enumerable.Group By Queryable.GroupBy
ToLookup	Inserts elements into a Lookup<TKey,TElement> (a one-to- many dictionary) based on a key selector function.	Enumerable.ToLook up

GroupBy 与 ToLookup 的区别

来自<https://www.jianshu.com/p/dbae3593e824>

ToLookup 和 GroupBy 一样，唯一不同的是GroupBy 是延迟执行，而 ToLookup 是立即执行。