C#知识点简单回顾(有图有真相)

1)传值调用与引用调用

using System;

class MethodCall
{
    public static void Main() 
    {
        /*
         * 参数类型分为 in, ref, out 三种，默认为 in。
         * in 类型在子方法中修改了对应变量后，主方法中的值不会发生改变。
         * ref 类型在子方法中修改了对应变量后，主方法中的值也会发生改变。
         * out 主方法中对应的变量不需要初始化。
         * 
         */        
        int a = 1, b = 2, c;
        Console.WriteLine("Before Method Call : a = {0}, b = {1}, c 未赋值", a, b);
        AMethod(a, ref b, out c);
        Console.WriteLine("After  Method Call : a = {0}, b = {1}, c = {2}", a, b, c);

        Console.Read();
    }

    public static void AMethod(int x, ref int y, out int z)
    {
        x = 110;
        y = 120;
        z = 119;
    }
}

效果图：

 2)打印三角形

using System;

public class Hello
{
    public static void Main()
    {
        Console.Write("请输入行数:");
        int lines = int.Parse(Console.ReadLine());
        Console.WriteLine("");

        for(int i=1; i<=lines ; i++)
        {
            for(int k=1; k<= lines-i; k++)
                Console.Write(" ");

            for(int j=1; j<=i*2+1; j++)
                Console.Write("*");
            Console.WriteLine("");
        }
        Console.ReadLine();
    }
}

效果图：

 3)递归求阶乘

using System;

class Factor
{
    public static void Main()
    {
        for(int i=1; i<=10; i++)
            Console.WriteLine("{0} 的阶乘是 {1}",i, Factorial(i));


        Console.Read();
    }
    public static long Factorial(long n)
    {
        if(n == 1)
            return 1;
        else
            return n * Factorial(n-1);
    }
}

效果图：

4)多态性

using System;

class Car
{
    public virtual void Drive()
    { Console.WriteLine("Drive Car"); }
}
class Truck : Car
{
    public override void Drive()
    { Console.WriteLine("Drive Truck");    }

}
class Client
{
    public static void Main()
    {
        Car c = new Truck();
        c.Drive();    //多态性决定着将调用Truck的Drive方法


        Console.Read();
    }
}

效果图：

5)方法重载

using System;

class Client
{
    public static void Main()
    {
        //重载是指方法名相同，方法的签名不同
        Console.WriteLine(Add(100,50));
        Console.WriteLine(Add("100","50"));

        Console.Read();
    }

    public static string Add(string a, string b)
    {
        return a + " add " + b;
    }

    public static int Add(int a, int b)
    {
        return a+b;
    }
}

效果图：

6)构造函数

using System;

public class Person
{
    public string name = "";
    public int age = 0;

    //默认构造函数
    public Person()
    {
    }

    //构造函数重载(1)
    public Person(int Age)
    {
        this.age = Age;
    }

    //构造函数重载(2)
    public Person(int Age, string Name)
    {
        this.age = Age;
        this.name = Name;
    }

    public void ShowInfo()
    {
        Console.WriteLine("姓名:" + name);
        Console.WriteLine("年龄:" + age);
    }
}

class Client
{
    public static void Main()
    {
        Person p1 = new Person();
        p1.ShowInfo();

        Console.WriteLine("*************************");

        Person p2 = new Person(25);
        p2.ShowInfo();

        Console.WriteLine("*************************");
        Person p3 = new Person(25, "爱智旮旯");
        p3.ShowInfo();



        Console.Read();
    }
}

效果图：

7)静态与非静态

using System;

class StaticHello
{
    public static void SayHello()
    { Console.WriteLine("Static Hello"); }
}

class NonStaticHello
{
    public void SayHello()
    { Console.WriteLine("Non Static Hello"); }
}

class Client
{
    public static void Main()
    {
        //静态方法调用应当使用 “类名.方法”
        StaticHello.SayHello();

        //非静态方法调用应当使用 “实例名称.方法”
        NonStaticHello h = new NonStaticHello();
        h.SayHello();


        Console.Read();
    }
}

效果图：

8)九九表

using System;

public class JiuJiuBiao
{
    public static void Main(string[] args)
    {
        int i,j;
        for(i=1; i<10; i++)
        {
            for(j=1; j<10; j++)
            {
                Console.Write("{0:D1}*{1:D1}={2,2}  ", i, j, i*j);
            }
            Console.WriteLine("");
        }
        Console.ReadLine();
    }
}

效果图：

9)冒泡法排序

using System;

class ArraySort
{
    public static void Main()
    {
        int[] d = {10,15,21,43,17,98,2,74,63,10};
        int temp;        

        //冒泡法排序
        for(int i=0; i<d.Length; i++)
            for(int j=i+1; j<d.Length; j++)
                if(d[i]<d[j])
                {
                    temp = d[i];
                    d[i]=d[j];
                    d[j]=temp;
                }

        //输出排序结果
        foreach(int i in d)
            Console.Write("{0}, ", i);



        Console.Read();
    }
}

效果图：

10)求质数

using System;

class Factor
{
    public static void Main()
    {
        for(int i=1; i<=100; i++)
            if(IsPrime(i))
                Console.WriteLine(i);


        Console.Read();
    }

    public static bool IsPrime(int n)
    {
        for(int i=2; i<=Math.Sqrt(n); i++)
            if(n%i == 0)
                return false;

        return true;
    }
}

效果图：

11)使用接口排序(1)

using System;
using System.Collections; 

public class Person : IComparable
{
    public int ID;
    public string Rank;

    public Person(int id, string rank)
    { this.ID=id; this.Rank = rank; }

    #region IComparable Members

    /*
     * IComparable 接口只有一个方法: CompareTo。CompareTo方法 
     * 只接收一个object类型的参数，这意味着它可以接收任何类
     * 型的数据（object是所有类的父类），这个方法会返回一
     * 整型数值，含义如下：
     * 
     * 1) 小于零，当前实例（this）小于obj对象 
     * 2) 等于零，当前实例（this）等于obj对象
     * 3) 大于零，当前实例（this）大于obj对象 
     * 
     * Int32,Int16...,String,Decimal等数据类型都已经实现了IComparable接口
     */
    public int CompareTo(object obj)
    {
        Person p = (Person)obj;
        return this.ID.CompareTo(p.ID);
    }

    #endregion
}

class SortArrayList 
{
    static void Main(string[] args) 
    {
        ArrayList list = new ArrayList();
        list.Add(new Person(6, "排长"));
        list.Add(new Person(3, "团长"));
        list.Add(new Person(4, "司令"));
        list.Add(new Person(5, "旅长"));
        list.Add(new Person(7, "连长"));
        list.Add(new Person(1, "军长"));
        list.Add(new Person(2, "营长"));
        list.Add(new Person(8, "师长"));

        list.Sort();

        Console.WriteLine("After Sorting");
        foreach (Person person in list) 
        {
            Console.WriteLine("ID: " + person.ID.ToString() + ", Rank: " + person.Rank);
        }
    }
}

效果图：

12)使用接口排序(2)

using System;
using System.Collections; 

public enum enuSortOrder
{IDAsc, IDDesc, RankAsc, RankDesc}

public class Person : IComparable
{
    public static enuSortOrder intSortOrder = enuSortOrder.IDAsc;

    public int ID;
    public string Rank;

    public Person(int id, string rank)
    { this.ID=id; this.Rank = rank; }

    #region IComparable Members

    /*
     * IComparable 接口只有一个方法: CompareTo。CompareTo方法 
     * 只接收一个object类型的参数，这意味着它可以接收任何类
     * 型的数据（object是所有类的父类），这个方法会返回一
     * 整型数值，含义如下：
     * 
     * 1) 小于零，当前实例（this）小于obj对象 
     * 2) 等于零，当前实例（this）等于obj对象
     * 3) 大于零，当前实例（this）大于obj对象 
     * 
     * Int32,Int16...,String,Decimal等数据类型都已经实现了IComparable接口
     */
    public int CompareTo(object obj)
    {
        Person p = (Person)obj;
        switch ((int)intSortOrder)
        {
            case (int)enuSortOrder.IDAsc:
                return this.ID.CompareTo(p.ID);
            case (int)enuSortOrder.IDDesc:
                return p.ID.CompareTo(this.ID);
            case (int)enuSortOrder.RankAsc:
                return RankCompare(this.Rank, p.Rank);
            case (int)enuSortOrder.RankDesc:
                return RankCompare(p.Rank, this.Rank);
            default:
                return this.ID.CompareTo(p.ID);
        }
    }

    private int RankCompare(string rank1, string rank2)
    {
        int intRank1 = ConvertRankToInt(rank1);
        int intRank2 = ConvertRankToInt(rank2);
        if(intRank1 < intRank2)
            return -1;
        else if(intRank1 == intRank2)
            return 0;
        else
            return 1;
    }

    private int ConvertRankToInt(string rank)
    {
        if(rank == "司令")
            return 8;
        else if(rank == "军长")
            return 7;
        else if(rank == "师长")
            return 6;
        else if(rank == "旅长")
            return 5;
        else if(rank == "团长")
            return 4;
        else if(rank == "营长")
            return 3;
        else if(rank == "连长")
            return 2;
        else
            return 1;
    }

    #endregion
}

class SortArrayList 
{
    static void Main(string[] args) 
    {
        ArrayList list = new ArrayList();
        list.Add(new Person(6, "排长"));
        list.Add(new Person(3, "团长"));
        list.Add(new Person(4, "司令"));
        list.Add(new Person(5, "旅长"));
        list.Add(new Person(7, "连长"));
        list.Add(new Person(1, "军长"));
        list.Add(new Person(2, "营长"));
        list.Add(new Person(8, "师长"));

        list.Sort();
        Console.WriteLine("Sort By ID Asc:");
        foreach (Person person in list) 
        {
            Console.WriteLine("ID: " + person.ID.ToString() + ", Rank: " + person.Rank);
        }

        Console.WriteLine("----------------------------");
        Console.WriteLine("Sort By ID Desc:");

        Person.intSortOrder = enuSortOrder.IDDesc;
        list.Sort();
        foreach (Person person in list) 
        {
            Console.WriteLine("ID: " + person.ID.ToString() + ", Rank: " + person.Rank);
        }

        Console.WriteLine("----------------------------");
        Console.WriteLine("Sort By Rank Asc:");

        Person.intSortOrder = enuSortOrder.RankAsc;
        list.Sort();
        foreach (Person person in list) 
        {
            Console.WriteLine("ID: " + person.ID.ToString() + ", Rank: " + person.Rank);
        }

        Console.WriteLine("----------------------------");
        Console.WriteLine("Sort By Rank Desc:");

        Person.intSortOrder = enuSortOrder.RankDesc;
        list.Sort();
        foreach (Person person in list) 
        {
            Console.WriteLine("ID: " + person.ID.ToString() + ", Rank: " + person.Rank);
        }
    }    
}

效果图：

13)属性、方法作用范围

using System;

class Base
{
    /*
     * public 的可访问范围是所有类
     * private 的可访问范围是当前类
     * protected 的可访问范围是当前类及其子类
     */
    public string name = "Tom";
    private double salary = 1500;
    protected int age = 20;

    public virtual void ShowInfo()
    {
        Console.WriteLine(this.name);    //可以，因为name是 public 型的
        Console.WriteLine(this.salary);    //可以，salary是private型，在Base类中可以访问
        Console.WriteLine(this.age);    //可以，因为age是protected型，在子类中可以访问
    }
}

class Derived : Base
{
    public override void ShowInfo()
    {
        Console.WriteLine(this.name);    //可以，因为name是 public 型的
        //Console.WriteLine(this.salary);    //不可以，salary是private型，超出Base就无法访问
        Console.WriteLine(this.age);    //可以，因为age是protected型，在子类中可以访问
    }
}

class Client
{
    public static void Main()
    {
        Base b = new Base();
        Console.WriteLine(b.name);    //可以，因为name是 public 型的
        //Console.WriteLine(this.salary);    //不可以，salary是private型，超出Base就无法访问
        //Console.WriteLine(this.age);    //不可以，因为age是protected型，Client不是Base的子类

        Console.WriteLine("==========================");
        b.ShowInfo();
        Console.WriteLine("==========================");
        Derived d = new Derived();
        d.ShowInfo();
    }
}

14)一加到一百

using System;

class SumToHundred
{
    public static void Main()
    {
        int sum=0;
        for(int i=1; i<=100; i++)
            sum += i;
        Console.WriteLine(sum);
    }
}

效果图：

15)字段与属性

using System;

class Account
{
    private double balance = 0;        //字段
    public double Balance            //属性
    {
        get { return balance; }
        set { balance = value;}
    }
    /*=============================================================
     * 我们可以通过修改get、set方法达到控制存取的目的。
     * 例如：
     * 
     * 1)只读属性
     * public double Balance            //属性
     * {
     *    get { return balance; }
     *    set { }
     * }
     * 
     * 2)读写控制
     * public double Balance
     * {
     *    get 
     *    {
     *       if(Console.ReadLine()=="1234")
     *          return balance;
     *       else
     *          return -9999999;
     *    }
     *    set { }
     * }
     * =============================================================
     */

    public void Deposit(double n)
    { this.balance += n; }

    public void WithDraw(double n)
    { this.balance -= n; }
}

class Client
{
    public static void Main()
    {
        Account a = new Account();
        a.Balance = 1000;    // 可以读写属性，因为属性Balance是public型的
        //a.balance = 1000;    //不可以读写字段，因为字段balance是private型的

        a.WithDraw(500);
        a.Deposit(2000);
        Console.WriteLine(a.Balance);
    }
}