C# 面向对象4 构造函数

构造函数

1.构造函数用来创建对象,并且可以在构造函数中对对象进行初始化.

(给对象的每个属性依次的赋值)

2.构造函数是用来创建对象的特殊方法:

  1.方法名和类名一样.

  2.没有返回值,连void都不用..

**创建对象的时候会执行构造函数.(静态类呢?静态类不创建对象)

3.new 关键字

Person zs = new Person();

new帮助我们做了3件事儿:

  1.在内存中开辟了一块空间

  2.在开辟的空间中创建对象

  3.调用对象的构造函数进行初始化

**所以构造函数必须是Public!

**构造函数可以有参数,new对象的时候传递函数参数即可.

4.构造函数可以重载,也就是有多个参数不同的构造函数.

**如果不指定构造函数,则类有一个默认的无参构造函数;

**如果指定了构造函数,则不再有默认的无参构造函数;

**如果类中已经有指定参数的构造函数,如果需要无参构造函数,则需要自己来写.

**构造函数的最大优点是,可以方便快捷的对对象初始化!!!

类代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _04面向对象练习
{
    public class Student
    {
        //字段,属性,方法,构造函数

        

        //构造函数
        public Student(string name,int age,char gender,int chinese,int math,int english)
        {
            //
            this.Name = name;
            this.Age = age;
            this.Gender = gender;
            this.Chinese = chinese;
            this.Math = math;
            this.English = english;
        }

        public Student(string name)
        {
            this.Name = name;
        }

        public Student()
        {
            Console.WriteLine("Hello!");
        }

        private string _name;
        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }

        private int _age;
        public int Age
        {
            get { return _age; }
            set {
                if (value < 0 || value > 100)
                    value = 0;

                _age = value; }
        }

        private char _gender;
        public char Gender
        {
            get {
                if(_gender !='男'&&_gender!='女')
                   return  _gender='男';

                return _gender; }
            set { _gender = value; }
        }

        private int _chinese;
        public int Chinese
        {
            get { return _chinese; }
            set { _chinese = value; }
        }

        private int _math;
        public int Math
        {
            get { return _math; }
            set { _math = value; }
        }

        private int _english;
        public int English
        {
            get { return _english; }
            set { _english = value; }
        }

        public void SayHello()
        {
            Console.WriteLine("我叫{0},我今年{1}岁了,我是{2}生",this.Name,this.Age,this.Gender);
        }

        public void ShowScore()
        {
            Console.WriteLine("我叫{0},我的总成绩是{1},平均成绩是{2}", this.Name, this.Chinese + this.Math + this.English, (this.Chinese + this.Math + this.English)/3);
        }

    }
}

main代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _04面向对象练习
{
    class Program
    {
        static void Main(string[] args)
        {

            Student a = new Student("zq", 31, '中', 100, 100, 100);
            //a.Name = "zq";
            //a.Age = 31;
            //a.Gender = '男';
            //a.Chinese = 90;
            //a.English = 89;
            //a.Math = 99;

            a.SayHello();
            a.ShowScore();

            Student b = new Student("junfeng",34,'女',50,50,50);
            //b.Name = "junfeng";
            //b.Age = 34;
            //b.Gender = '女';
            //b.Chinese = 61;
            //b.Math = 90;
            //b.English = 100;

            b.SayHello();
            b.ShowScore();


            Console.ReadKey();
        }
    }
}