第十一章习题

习题

知识点一

集合CollectionBase
键控集合DictionaryBase

知识点二

迭代器
IEnumerable 与 IEnumerator
迭代一个类，可以使用方法GetEnumerator()，返回类型IEnumerator；
迭代一个类成员，可以使用方法GetEnumerable()，返回类型IEnumerable

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Exercise
{
    class Program
    {
        static void Main(string[] args)
        {
            Person p1 = new Person("1", 10);
            Person p2 = new Person("2", 89);
            Person p3 = new Person("3", 58);
            Person p4 = new Person("4", 49);
            People people = new People();
            people.Add(p1);
            people.Add(p2);
            people.Add(p3);
            people.Add(p4);
            foreach (int i in people.GetAges())
            {
                Console.WriteLine($"i:{i}");
            }
            Console.ReadKey();
        }
    }
    public class Person
    {
        private string name;
        private int age;
        public string Name { get => name; set => name = value; }
        public int Age { get => age; set => age = value; }
        public Person(string name, int age)
        {
            this.age = age;
            this.name = name;
        }
        public Person()
        {
        }
        public static bool operator >(Person per1, Person per2) => per1.age > per2.age;
        public static bool operator <(Person per1, Person per2) => per1.age > per2.age;
        public static bool operator >=(Person per1, Person per2) => !(per1 < per2);
        public static bool operator <=(Person per1, Person per2) => !(per1 > per2);
    }
    public class People : DictionaryBase, ICloneable
    {
        public void Add(Person newPerson)
        {
            Dictionary.Add(newPerson.Name, newPerson);
        }
        public void Remove(string personName)
        {
            Dictionary.Remove(personName);
        }
        public Person this[string personName]
        {
            get { return (Person)Dictionary[personName]; }
            set { Dictionary[personName] = value; }
        }
        public Person[] GetOldest()
        {
            Person oldestPerson = null;
            People oldestPeople = new People();
            Person currentPerson;
            foreach (DictionaryEntry p in Dictionary)
            {
                currentPerson = p.Value as Person;
                if (oldestPerson == null)
                {
                    oldestPerson = currentPerson;
                }
                else
                {
                    if (currentPerson > oldestPerson)
                    {
                        oldestPeople.Clear();
                        oldestPeople.Add(currentPerson);
                    }
                    else
                    {
                        if (currentPerson >= oldestPerson)//没有定义‘==’运算哦
                        {
                            oldestPeople.Add(currentPerson);
                        }
                    }
                }
            }
            Person[] returnPersons = new Person[Dictionary.Count];
            for (int i = 0; i < Dictionary.Count; i++)
            {
                returnPersons[i] = (Person)Dictionary[i];
            }
            Dictionary.CopyTo(returnPersons, 0);
            return returnPersons;
        }
        public object Clone()
        {
            //People newPeople = new People();
            //foreach (Person per in List)
            //{
            //    newPeople.List.Add(new Person(per.Name, per.Age));
            //}
            //return (object)newPeople;
            People clonePeople = new People();
            Person currentPerson, newPerson;
            foreach (DictionaryEntry p in Dictionary)
            {
                currentPerson = p.Value as Person;
                newPerson = new Person();
                newPerson.Name = currentPerson.Name;
                newPerson.Age = currentPerson.Age;
                clonePeople.Add(newPerson);
            }
            return clonePeople;
        }
        public IEnumerable GetAges()
        {
            foreach (Object per in Dictionary)
            {
                yield return (per as Person).Age;
            }
        }
    }
}