Is it compulsory to present a constructor in base class with 0 argument

Question

public class myBaseClass { public myBaseClass() { code } public myBaseClass(int age) { code } } public class myDerivedClass : myBaseClass { public myDerivedClass() { code } public myDerivedClass(int age) { code } } myDerivedClass obj = new myDerivedClass(); This is original code. If I make comment to base class constructor without argument i.e. /*public myBaseClass() { code }*/ and now run the same code  error comes No overload for method 'myBaseClass' takes '0' arguments Why? Is it compulsory that if any constructor is present with one parameter in base class then constructor with 0 arguments should also be present.

amit_gupta14 · Answer

using System; public class myBaseClass { /* public myBaseClass() { Console.WriteLine(Base class constructor without argument); } */ public myBaseClass(int Age) { Console.WriteLine(Base class constructor with 1 argument); } } public class myDerivedClass : myBaseClass { public myDerivedClass() { Console.WriteLine(Derive class constructor without argument); } public myDerivedClass(int Age) { Console.WriteLine(Derive class constructor 1 argument); } } class Class1 { [STAThread] static void Main(string[] args) { myDerivedClass obj = new myDerivedClass(); } } I am fully satisfied with ur answer but why above code is not working. When I use myDerivedClass obj = new myDerivedClass(); or myDerivedClass obj = new myDerivedClass(10); It throws the same type of error:No overload for method 'myBaseClass' takes '0' arguments Note:Base class constructpr with 0 arguments is commented

bilnaad · Answer

if you add a constructor yourself. I mean with or without parameters the compiler will not add it's default constructor. When you instranciate a class object. You have to pass an parameter list new myclass() or new myclass(arg1 arg2). With this parameter list the compiler will look for a signature that is identical to you parameter list. If there isn't one found the compiler generates an error. Also it's a good and helpfull practice to chain the constructor. This is also very helpfull with methods. It prevents you to write duplicate code ^_^ (It's overloading but chained) example of chaining: class SprayCan { private Color color; private float radius; //1 public SprayCan() :this(Color.Black){}//calls 2 //2 public SprayCan(Color color) :this(color 1.0f){}//calls 3 //3 public SprayCan(Color color float radius) { this.color = color; this.radius = radius; } }

amit_gupta14 · Answer

1. That's good thing. But in my example If I comment base class constructor (of 0 arguments)still one constructor with 1 argument is present. So compiler will not add parameterless constructor. Am I right? 2. If I am using derive_class d1=new derive_class() or derive_class d1=new derive_class(10) And base class constructor (of 0 arguments) is coomented then why compiler throws the error. 3. When we call a derive class constructor with or without arguments it always look for 1st constructor present in base class whether 0 arguments or with arguments? Am I right? I mean is there any sequence of invoking base class constructor in terms of arguments

bilnaad · Answer

No it's not compulsory. The only thing you should keep in mind is when you add no constructor to a class the compiler adds a parameterless constructor in the class which initializes all fields to it's default values. Note that when you add one+ constructor to the class. The default one is not added by the compiler.