前言： 完全是我在學習過程中記錄的筆記，只不過分享一下讓很多剛開始學習.net編程的人能夠很快的學會C#語言

多態的一些說明

?(1) 多態就是為了程序的可擴展性

?(2)多態的使用：將不同的對象當作父類來看，屏蔽掉各個對象間的不同，寫出通用代碼，做出通用編程，同樣調用不同結果，以適應需求的不斷變化

?(3)ToString方法有Object提供，使得所有的類型均可以使用Console.WriteLine()方法

??????????? class Person

??????????? {

?????????????????? public string Name { get; set; }

?????????????????? public int Age { get; set; }

?????????????????? //當寫第三個的時候寫入下面的方法

?????????????????? public override string ToString()

?????????????????? {

????????????????????????? return Name;

?????????????????? }

??????????? }

??????????? class Program

??????????? {

?????????????????? static void Main(string[] args)

?????????????????? {

????????????????????????? int[] nums = { 1, 34, 4, 65, 7, 87, 454 };

????????????????????????? Console.WriteLine(nums);

????????????????????????? //輸出:System.Int32[]

????????????????????????? //準備對象

????????????????????????? Person p = new Person();

????????????????????????? p.Name = "韓迎龍";

????????????????????????? p.Age = 19;

????????????????????????? Console.WriteLine(p);

????????????????????????? //輸出:智能機器.Person

????????????????????????? //第三個

????????????????????????? Person p1 = new Person();

????????????????????????? p1.Name = "韓迎龍";

????????????????????????? p1.Age = 19;

????????????????????????? Console.WriteLine(p);

????????????????????????? //輸出張三

????????????????????????? Console.ReadKey();

?????????????????? }

??????????? }

?(4)多態的保障

??????????? 1)繼承，相同名字的方法(重載不算)

??????????? 2)里氏轉換原則

?(5)is和as

??????????? 1)判斷父類繼承

??????????? 2)判斷接口實現

??????????? 3)判斷拆箱和裝箱

　　2.多態實現計算器

(1) 新建一個控制臺應用程序，起名為多態計算器(2)添加一個CalculstingWay類，表示計算的方法/// <summary>/// 計算機的計算/// </summary>class CalculstingWay{int num1;int num2;public int Num1{get { return num1; }set { num1 = value; }}public int Num2{get { return num2; }set { num2 = value; }}public CalculstingWay(int n1, int n2){num1 = n1;num2 = n2;}public virtual int Calculating(){//這個方法是需要子類重寫的return 0;}}(3)添加一個Add類，表示實現加法的計算/// <summary>/// 提供加法計算的方法/// </summary>class Add:CalculstingWay{public Add(int n1, int n2): base(n1, n2){}public override int Calculating(){return base.Num1 + base.Num2;}} (4)添加一個Sub類，表示實現減法的計算/// <summary>/// 提供減法計算的方法/// </summary>class Sub : CalculstingWay{public Sub(int n1, int n2): base(n1, n2){}public override int Calculating(){return base.Num1 - base.Num2;}} (5)添加一個Multi類，表示實現乘法的計算/// <summary>/// 提供乘法計算的方法/// </summary>class Multi : CalculstingWay{public Multi(int n1, int n2): base(n1, n2){}public override int Calculating(){return base.Num1 + base.Num2;}} (6)添加一個Div類，表示實現除法的計算/// <summary>/// 提供除法計算的方法/// </summary>class Div : CalculstingWay{public Div(int n1, int n2): base(n1, n2){}public override int Calculating(){return base.Num1 + base.Num2;}}
(7)添加一個Calculator類，表示計算器類/// <summary>/// 表示計算器/// </summary>class Calculator{//可以進行計算的對象CalculstingWay cal;public Calculator(int num1, int num2, string oper){switch (oper){case "+":cal = new Add(num1, num2);break;case "-":cal = new Sub(num1, num2);break;case "*":cal = new Multi(num1, num2);break;case "/":cal = new Div(num1, num2);break;default:cal = null;break;}}public int jisuan(){if (cal != null){return cal.Calculating();}else{return -1;}}}

　　3.?抽象方法

?(1) 父類提供一個可以被重寫的方法，有子類重寫，通過父類，new子類來調用

?(2)父類不需要方法體

?(3)語法：[public] abstract 返回類型 方法名(參數);

?????????????????? 和方法相比有以下幾點需要注意的：

?????????????????? 1)去掉方法體，直接在圓括號結束的時候加分號

?????????????????? 2)加上abstract進行修飾

?(4)抽象方法只允許在抽象類中存在

??????????? 1)只要在class關鍵字前面用abstract修飾即可

?????????????????? abstract class 類名

?????????????????? {

????????????????????????? //成員

?????????????????? }

(5)抽象方法，抽象類就是為了被子類繼承，重寫的

abstract class Animal{public abstract void Shout();}class Dog : Animal{public override void Shout(){Console.WriteLine("財旺福王運道旺");}}class Cat : Animal{public override void Shout(){Console.WriteLine("喵喵喵");}}class Program{static void Main(string[] args){Animal[] animals = {new Dog(),new Cat() };for (int i = 0; i < animals.Length; i++){animals[i].Shout();}Console.ReadKey();}}

?(6)抽象方法的細節

??????????? 1)抽象類中可以包含什么東西？

?????????????????? ->比一般類多了抽象成員

?????????????????? ->抽象成員有有什么：方法，屬性，索引器，事件聲明

??????????? 2)抽象類不允許實例化，不能new

??????????? 3)抽象類可以有構造方法

??????????? 4)抽象類可以來源于非抽象類

?????????????????? class MyBase

?????????????????? {

?????????????????? }

?????????????????? abstract class Test : MyBase

?????????????????? {

????????????????????????? public abstract void Func();

?????????????????? }

?????????????????? class MySub : Test

?????????????????? {

????????????????????????? public override void Func()

????????????????????????? {

???????????????????????????????? Console.WriteLine("抽象類可以來源于非抽象類");

????????????????????????? }

?????????????????? }

??????????? 5)抽象類必須被子類重寫，除非子類也是抽象的

?(7)練習：有一個形狀Shape類，派生出圓Circle，矩形Rectangle和正方形Square,分別計算他們的面積Area和周長Perimeter?

1)新建一個控制臺項目:起名為多態小案例2)添加一個Shape類，實現計算面積和周長的方法abstract class Shape{public abstract double GetArea();public abstract double GetPerimeter();}3)添加一個Circle類，實現計算圓的面積和周長class Circle : Shape{int r;public Circle(int r){this.r = r;}public override double GetArea(){return Math.PI * Math.Pow(r, 2);}public override double GetPerimeter(){return 2 * Math.PI * r;}}4)添加一個類，實現計算矩形的面積和周長class Rectangle : Shape{double widthX;double heightY;public Rectangle(double widthX, double heightY){this.widthX = widthX;this.heightY = heightY;}public override double GetArea(){return widthX * heightY;}public override double GetPerimeter(){return 2 * (widthX + heightY);}}5)添加一個類，實現計算正方形的面積和周長class Square : Shape{double length;public Square(double length){this.length = length;}public override double GetArea(){return Math.Pow(length, 2);}public override double GetPerimeter(){return 4 * length;}}class Square1 : Rectangle{public Square1(double length): base(length, length){}}6)在Main方法中實現的代碼如下：class Program{static void Main(string[] args){Circle circle = new Circle(5);Console.WriteLine(circle.GetArea().ToString("0.00"));Console.WriteLine(circle.GetPerimeter().ToString("0.00"));Rectangle rec = new Rectangle(5, 10);Console.WriteLine(rec.GetArea());Console.WriteLine(rec.GetPerimeter());Square square = new Square(5);Console.WriteLine(square.GetArea());Console.WriteLine(square.GetPerimeter());Square1 sqr = new Square1(5);Console.WriteLine(sqr.GetArea());Console.WriteLine(sqr.GetPerimeter());}}

?(8)抽象屬性

??????????? 1)使用abstract修飾

??????????? 2)去掉方法體

??????????? 3)語法：public abstract 返回類型 屬性

????????????????????????? {

???????????????????????????????? get;

???????????????????????????????? set;

????????????????????????? }

??????????? 4)自動屬性必須包含get,set方法

??????????? 5)抽象屬性可以定義只讀，只寫，

?(9)由子類實現抽象屬性的方法

??????????? 1)用override重寫屬性

??????????? 2)添加一個字段，使用屬性

面向對象計算器(簡單工廠計算器)

(1) 新建一個控制臺應用程序，起名為：簡單工廠計算器(最好寫成英文的，我是為了學習直接寫成中文的了) (2)新建一個CalculatingWay類，實現計算機的父類計算/// <summary>/// 計算機的計算/// </summary>abstract class CalculstingWay{int num1;int num2;public int Num1{get { return num1; }set { num1 = value; }}public int Num2{get { return num2; }set { num2 = value; }}public CalculstingWay(int n1, int n2){num1 = n1;num2 = n2;}public abstract int Calculating();}(3)新建一個Add類，/// <summary>/// 提供加法計算的方法/// </summary>class Add:CalculstingWay{public Add(int n1, int n2): base(n1, n2){}public override int Calculating(){return base.Num1 + base.Num2;}}(4)新建一個Sub類，/// <summary>/// 提供減法計算的方法/// </summary>class Sub : CalculstingWay{public Sub(int n1, int n2): base(n1, n2){}public override int Calculating(){return base.Num1 - base.Num2;}}(5)新建一個Multi類，/// <summary>/// 提供乘法計算的方法/// </summary>class Multi : CalculstingWay{public Multi(int n1, int n2): base(n1, n2){}public override int Calculating(){return base.Num1 + base.Num2;}} (6)新建一個Div類，/// <summary>/// 提供除法計算的方法/// </summary>class Div : CalculstingWay{public Div(int n1, int n2): base(n1, n2){}public override int Calculating(){return base.Num1 + base.Num2;}} (7)新建一個Factory類static class Factory{public static CalculstingWay GetCalculator(int n1,int n2,string oper){switch (oper){case "+":return new Add(n1, n2);case "-":return new Sub(n1, n2);case "*":return new Multi(n1, n2);case "/":return new Div(n1, n2);default:return null;}}} (8)在Main方法中寫入如下這段代碼：class Program{static void Main(string[] args){//提示用戶輸入Console.Write("請用戶輸入第一個數字：");int num1 = GetInputNum();Console.Write("請用戶輸入第一個數字：");int num2 = GetInputNum();Console.Write("請輸入運算符");string oper = Console.ReadLine();//開始生產CalculstingWay cal = Factory.GetCalculator(num1, num2, oper);//開始投入使用if (cal != null){int res = cal.Calculating();Console.WriteLine("{0}{1}{2}={3}", num1, oper, num2, res);}else{Console.WriteLine("運算符有誤");}}public static int GetInputNum(){return GetInputNum(int.MinValue, int.MaxValue);}/// <summary>/// 完成int類型數據的輸入，并返回，要求輸入的數字在0到給定的數字之間/// </summary>/// <param name="max">給定的數字的上限</param>/// <returns></returns>public static int GetInputNum(int max){return GetInputNum(0, max);}/// <summary>/// 完成int數字的輸入，要求在給定范圍之間/// </summary>/// <param name="min">給定范圍的下線</param>/// <param name="max">給定范圍的上線</param>/// <returns></returns>public static int GetInputNum(int min, int max){string str = Console.ReadLine();int num;while (true){try{num = Convert.ToInt32(str);if (num > min && num < max){break;}Console.Write("輸入數字不再{0}到{1}之間，請重新輸入", min, max);str = Console.ReadLine();}catch{Console.Write("輸入有誤，請重新輸入");str = Console.ReadLine();}}return num;}}

轉載于:https://www.cnblogs.com/hanyinglong/archive/2012/10/02/2710298.html

總結

以上是生活随笔為你收集整理的C#基础系列第五篇的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。