C#中子类构造函数

　　在C#中,一个子类继承父类后,两者的构造函数又有何关系??

　1.隐式调用父类构造函数

 ----------------父类

public class Employee   
    {
       public Employee(){
           Console.WriteLine("父类无参对象构造执行!");
   }
       public Employee(string id, string name, int age, Gender gender)
       {
           this.Age = age;
           this.Gender = gender;
           this.ID = id;
           this.Name = name;
       }
        protected string ID { get; set; }       //工号
        protected int Age { get; set; }         //年龄
        protected string Name { get; set; }     //姓名
        protected Gender Gender { get; set; }   //性别
    }

----------------------子类

public class SE : Employee
    {
        public SE() { } //子类
        public SE(string id, string name, int age, Gender gender, int popularity)
        {
            this.Age = age;
            this.Gender = gender;
            this.ID = id;
            this.Name = name;
            this.Popularity = popularity;
        }
        private int _popularity;
        //人气
        public string SayHi()
        {
            string message;
            message = string.Format("大家好,我是{0},今年{1}岁,工号是{2},我的人气值高达{3}!", base.Name, base.Age, base.ID, this.Popularity);
            return message;
        }
        public int Popularity
        {
            get { return _popularity; }
            set { _popularity = value; }
        }
    }

--------------------Main函数中调用

 static void Main(string[] args)
        {
            SE se = new SE("112","张三",25,Gender.male,100);
            Console.WriteLine(se.SayHi());
            Console.ReadLine();
}

-----------------运行结果

由上可知

创建子类对象时会首先调用父类的构造函数,然后才会调用子类本身的构造函数.
如果没有指明要调用父类的哪一个构造函数,系统会隐式地调用父类的无参构造函数

 

2.显式调用父类构造函数

 

C#中可以用base关键字调用父类的构造函数.只要在子类的构造函数后添加":base(参数列表)",就可以指定该子类的构造函数调用父类的哪一个构造函数.
这样可以实现继承属性的初始化,然后在子类本身的构造函数中完成对子类特有属性的初始化即可.

------------------子类代码变更为其余不变 

  public class SE : Employee
    {
        public SE() { } //子类
        public SE(string id, string name, int age, Gender gender, int popularity):base(id,name,age,gender)
        {
            //继承自父类的属性
            //调用父类的构造函数可以替换掉的代码
            //this.Age = age;
            //this.Gender = gender;
            //this.ID = id;
            //this.Name = name;
            this.Popularity = popularity;
        }
        private int _popularity;
        //人气
        public string SayHi()
        {
            string message;
            message = string.Format("大家好,我是{0},今年{1}岁,工号是{2},我的人气值高达{3}!", base.Name, base.Age, base.ID, this.Popularity);
            return message;
        }
        public int Popularity
        {
            get { return _popularity; }
            set { _popularity = value; }
        }


    }

运行结果为

注意:base关键字调用父类构造函数时,只能传递参数,无需再次指定参数数据类型,同时需要注意,这些参数的变量名必须与父类构造函数中的参数名一致.如果不一样就会出现报错