LINQ笔记-介绍

let：在linq中定义变量，可以重复使用

var lowercaseStudentNames = from s in studentList
let lowercaseStudentName = s.StudentName.ToLower()
where lowercaseStudentName.StartsWith("r")
select lowercaseStudentName;

into：创建一个临时标识符，该标识符可以存储group、join、select子句结果

var teenAgerStudents = from s in studentList
where s.age > 12 && s.age < 20
select s
into teenStudents
where teenStudents.StudentName.StartsWith("B")
select teenStudents;

SelectMany():返回列表中属性的集合（可将集合属性拼成一个大集合返回）

var list2 = teachers.SelectMany(teacher => teacher.Students);