C#使用this关键字实现串联构造函数调用方法

public class Person
{       
        public string personName;
        //定义年龄为可空类型,这样就可以赋予其null值
        public int? personAge;

        //下面前三个构造函数都是去调用参数最多的第四个构造函数,只取它们所需要的部分参数即可
        //这样的做法就是this串联构造函数
        public Person():this("",0)
        {
           
        }

        public Person(string name):this("evan",null)
        {
           
        }

        public Person(int age):this("",20)
        {
           
        }

        public Person(string name, int? age)
        {
            this.personName = name;
            //通过 ?? 判断传入的age是否null值
            //如果属于null值,则赋值100
            this.personAge = age ?? 100;
        }

        public void Display()
        {
            Console.WriteLine("Name:{0},Age:{1}/n", personName, personAge);
        }       
}

static void Main(string[] args)
{
        Person per1 = new Person();
        per1.Display();           

        Person per2 = new Person(20);
        per2.Display();           

        Person per3 = new Person("evan");
        per3.Display();           

        Person per4 = new Person("evan", 20);
        per4.Display();

        Console.ReadLine();           
}