c# lambda表达式学习(3)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Text;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main()
        {
            var students = new List()
            {
                new Student("john", 18),
                new Student("cathy", 22),
                new Student("tom", 20)
            };

            //定义输出函数
            Action print = student => Console.WriteLine(string.Concat(student.Name, ":", student.Age));

            //循环输出 
            Console.WriteLine("全部输出:");
            students.ForEach(print);
            Console.WriteLine("-------------------");

            //条件输出
            Console.WriteLine("输出年龄大于21的:");
            students.FindAll(student => student.Age > 21).ForEach(print);
            Console.WriteLine("-------------------");

            //排序输出
            Console.WriteLine("年龄从小到大排序后输出");
            students.Sort((f1, f2) => f1.Age.CompareTo(f2.Age));
            students.ForEach(print);
            Console.WriteLine("-------------------");

            //添加一个新学生
            students.Add(new Student("jerry", 20));

            //先进行分组，再进行投影
            Console.WriteLine("先进行分组，再进行投影");
            var result = students.GroupBy(x => x.Age).Select(x => string.Concat(x.Key, ":", x.Count()));
            result.ToList().ForEach(x => Console.WriteLine(x.ToString()));//循环输出得到结果
            Console.WriteLine("-------------------");
 
            Console.Read();
        }

        public class Student
        {
            public Student(string name, int age)
            {
                this.Name = name;
                this.Age = age;
            }

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