C ＃ use this keyword to concatenate constructor to call method

         This article gives an example of C# Use this Keyword implements the concatenation constructor to call the method . Share with you for your reference . The specific analysis is as follows ：

If you need to implement multiple custom constructors in a class , The usual approach is to implement the respective business logic in the constructor , If the implementation of these business logic is not entirely different , Obviously not in line with oop Programming idea , Extremely difficult to maintain , Of course , We can also encapsulate the same logic into a method , But there is a more reasonable and simple way , Let's go through this Keyword to implement the concatenation constructor to do a simple example .

The sample code is as follows :

public class Person

{        

        public string personName;

        // Define age as nullable type , So you can give it null value 

        public int? personAge;
        // The first three constructors below are the fourth constructor with the most parameters to call , Just take some of the parameters they need 

        // The way to do it is this Concatenation constructor 

        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;

            // adopt  ??  Judge the incoming age whether null value 

            // If it belongs to null value , Then assign 100

            this.personAge = age ?? 100;

        }
        public void Display()

        {

            Console.WriteLine("Name:{0},Age:{1}\n", personName, personAge);

        }        

}

The main function call is as follows :

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();            

}

This approach is to let a constructor that accepts the most parameters do " Primary constructor ", And implement the necessary business logic in the main constructor , The rest of the constructors just use this Keyword forwards the passed in parameters to the main constructor , And provide other necessary parameters , It looks like , What we need to worry about in our whole class is the main constructor , Other constructors can basically be empty .

Be careful : If there is logic to implement each other in the constructor chain , In fact, it is the code that executes the main constructor first , Then execute their respective logic , Use this method , The real work is left to a constructor , Class definitions will be simpler 、 Easier to maintain 、 Simplifies programming tasks .