写几个linq的代码示范

1. 查询数组中的偶数：

int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
var evenNumbers = numbers.Where(n => n % 2 == 0);

2. 查询字符串列表中长度大于等于5的字符串：

List<string> fruits = new List<string> { "apple", "banana", "orange", "grape", "kiwi" };
var longFruits = fruits.Where(f => f.Length >= 5);

3. 查询学生列表中年龄小于20岁的学生：

public class Student
{
    public string Name { get; set; }
    public int Age { get; set; }
}

List<Student> students = new List<Student>
{
    new Student { Name = "Tom", Age = 18 },
    new Student { Name = "Mary", Age = 21 },
    new Student { Name = "John", Age = 19 },
    new Student { Name = "Alice", Age = 22 }
};

var youngStudents = students.Where(s => s.Age < 20);

4. 查询员工列表中薪水大于5000的员工姓名：

public class Employee
{
    public string Name { get; set; }
    public int Salary { get; set; }
}

List<Employee> employees = new List<Employee>
{
    new Employee { Name = "Tom", Salary = 6000 },
    new Employee { Name = "Mary", Salary = 4500 },
    new Employee { Name = "John", Salary = 5500 },
    new Employee { Name = "Alice", Salary = 5000 }
};

var highSalaryEmployees = employees.Where(e => e.Salary > 5000).Select(e => e.Name);