Lambda表达式(lambda expression)⭐⭐⭐⭐⭐

lambda表达式(lambda expression)实际上是匿名函数一种表示形式，

即没有函数名的函数:参数列表=>表达式或语句块，在我看来主要目是为了简化代码编写，提高代码可读性而提供的语法糖。

　　C#中lambda表达式使用“=>”运算符表示，可读作“goes to”，

多参数多语句时用“（x,y）=>{语句块};”参数和语句块分别需要用小括号和大括号括起，

单参数单语句则可以“x=>语句;”无括号；无参数则表示为()=>表达式.

delegate void delegateLambda();
delegate void delegateLambda2(int x);
delegate void delegateLambda3(int x, int y);
private void btnCalculate_Click(object sender, EventArgs e)
{
    delegateLambda lam = () => MessageBox.Show("无参数lambda表达式");
    lam();
    delegateLambda2 lam2 = x =>
    {
        MessageBox.Show("单一参数lambda表达式x=:" + x.ToString());
    };
    lam2(50);
    delegateLambda3 lam3 = (x, y) =>
    {
        string result = (x + y).ToString();
        MessageBox.Show(result);
    };
    lam3(10, 20);
}

也可通过lambda表达式实现委托：

无论传统匿名方法还是Lambda 表达式实现的委托，

原理都是在编译过程中，创建了一个静态的方法实例委托的对象。

也就是说匿名方法和Lambda 表达式在CIL中都是采用命名方法实例化委托。

public partial class MainDisplay : Form
    {
        public MainDisplay()
        {
            InitializeComponent();
        }

        List<Student> studentList = new List<Student>();
        private void MainDisplay_Load(object sender, EventArgs e)
        {
            Student s1 = new Student() { Name = "张三", Id = "1", age = 13, ClassId = "5", Sex = "男" };
            Student s2 = new Student() { Name = "李四", Id = "2", age = 14, ClassId = "5", Sex = "男" };
            Student s3 = new Student() { Name = "王五", Id = "3", age = 17, ClassId = "2", Sex = "男" };
            Student s4 = new Student() { Name = "赵六", Id = "4", age = 16, ClassId = "2", Sex = "女" };
            studentList.Add(s1);
            studentList.Add(s2);
            studentList.Add(s3);
            studentList.Add(s4);
        }

        private void btnSearch_Click(object sender, EventArgs e)
        {
            List<Student> student=new List<Student>();
            //查询年龄大于30的学生
            student = studentList.Where(Stu => Stu.age > 15).ToList();
            foreach (Student stu in student)
            {
                MessageBox.Show(stu.Name);
            }
        }
    }

    public class Student
    {
        public string Id { get; set; }

        public string Name { get; set; }

        public string Sex { get; set; }

        public int age { get; set; }

        public string ClassId { get; set; }
    }

Lambda表达式(lambda expression)⭐⭐⭐⭐⭐

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