9、派生类的构造函数

语法:

  public DerivedClass ():base(){}

**tips: ** 如果不显式声明调用父类的无参构造函数（base()），那么默认会调用父类的无参构造函数。

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无参 Example

 class BaseClass
    {
        public BaseClass() {
            Console.WriteLine("BaseClass");
        }
    }

 class DerivedClass:BaseClass
    {
        public DerivedClass ():base() { // 因为是无参数，所以`:base()`默认可以不写
            Console.WriteLine("DerivedClass");
        } 
    }

  class Program
    {
        static void Main(string[] args)
        {
            DerivedClass derived = new DerivedClass();
            // 先调用base的构造方法，再调用子类的构造方法

            Console.ReadKey();
        }
    }

---

有参数Example:

 class BaseClass
    {
        private int x;
        public BaseClass() {
            Console.WriteLine("BaseClass");
        }
        public BaseClass(int x) {
            this.x = x;
        }
    }

class DerivedClass:BaseClass 
 {
        private int y;
        public DerivedClass ():base() {
            Console.WriteLine("DerivedClass");
        }
        public DerivedClass(int x, int y) : base(x) { // `base中的x就是前面的x`
            this.y = y;
            Console.WriteLine("x=" + x + ",  y=" + y);
        }
 }

class Program
    {
        static void Main(string[] args)
        {

            DerivedClass initDerived = new DerivedClass(5, 10);

            Console.ReadKey();
        }
    }