c#-4.0 - 性能问题 : How to execute Two lambda expression at once?。使用了 "Contains"和 "Any"运算符

Question

示例代码

var Ids = _db.Projects.Where(Project=>Project.Title!="test23rdoct")
    .Select (pro => pro.Id);

Expression<Func<Company, bool>> masterExpression = 
    Company => Company.Participants.Any(part => ids.Contains(part.Project.Id));

IQueryable<Object> queryEntity = _db.Companies.Where(masterExpression)

上述查询执行两次。在服务器中存储 id(有时 id 超过 50k 计数)。它会导致性能问题。有人可以建议如何组合这两个查询并立即执行吗？

Answer 1

怎么样:

var queryEntity = _db.Companies.Where(c => c.Partipants.Any(p => p.Project.Title != "test23rdoct"));

编辑 :
对于复杂的查询，您还可以拆分:

Func<Project, bool> projectFilter = Project => ((Compare(Convert(Project.Title), "a") > 0) AndAlso ((Convert(Project.Title) != "test23rdoct") AndAlso
(Project.Participants.Any(Participant => (Compare(Convert(Participant.ParticipantRole.Name), "Finance") > 0)) AndAlso 
(Project.Participants.Any(Participant => (Convert(Participant.Person.FirstName) != "test1")) AndAlso 
Project.Participants.Any(Participant => (Compare(Convert(Participant.Company.Name), "test") > 0))))));

然后做:

var queryEntity = _db.Companies.Where(c => c.Partipants.Any(p => projectFilter(p.Project));