EF中的Join和Contains的区别是什么

Question

听说
List<int> lstBizIds = new List<int>() { 1, 2, 3, 4, 5 };
List<int> lstProjectIds = context.Projects.Where(x =>lstBizIds.Contains(x.businessId)).Select(x => x.projectId).ToList();
会翻译成sql 是 in
SELECT Id FROM ProjectsWHERE UserId IN (1, 2, 3, 4, 5, 6)

而

List<int> lstBizIds = new List<int>() { 1, 2, 3, 4, 5 };
List<int> lstProjectIds = context.Projects.Join(lstBizIds, p => p.businessId, u => u, (p, u) => p.projectId).ToList();
会翻译成sql 是
SELECT Id
FROM Projects
INNER JOIN (VALUES (1), (2), (3), (4), (5)) AS Data(Item) ON Projects.UserId = Data.Item

但是我用join的时候，sql server 监听数据库的sql语句时，join反而是
SELECT Id FROM Projects 的
而且在使用ToListAsync等异步方法的时候，Join性能很差，用Contains反而会很好。这是为什么呢

Answer 1

就和sql里的 join和 like '%hello%'的区别

Answer 2

Join：连接，返回的T where T is class；Contains：（是否）包含，返回 bool；

Answer 3

上面的查询场景完全不需要用 Join