CODEWITHSUNDEEP
c#.net
Bluemarble
Bluemarble

Reputation: 2059

C# unable to call protected method from void main

I have the following code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    abstract class parent
    {
        public abstract void printFirstName();

        protected virtual void printLastName()
        {
            Console.WriteLine("Watson");
        }

        protected void printMiddlename()
        {
            Console.WriteLine("Jane");
        }
    }

    class child: parent
    {
        public override void printFirstName()
        {
            Console.WriteLine("Mary");
        }

        protected override void printLastName()
        {
            Console.WriteLine("Parker");
        }

        public void getMiddleName()
        {
            printMiddlename();
        }
    }


    class Program: child
    {
        static void Main(string[] args)
        {
            child ch = new child();

            ch.printFirstName();
            ch.getMiddleName();
            //ch.printLastName();

            Console.Read();
        }
    }
}

This code runs properly and prints Mary Jane

However, when I uncomment ch.printLastName(); it showscompile error:

enter image description here

Why cant my Program Class call protected method of Child Class? especially when The child class has no problem calling the protected method (printMiddleName) of Parent class?

Upvotes: 0

Views: 4811

Answers (6)

René Vogt
René Vogt

Reputation: 43876

I guess you are confusing inheritance and access levels.

Your Program class inherits the printFirstName method from child. So inside your Program class you can access that method:

class Program : child
{
    void Method() { this.printFirstName(); }
}

From outside a class you cannot access protected methods. But from inside a class you can access the protected methods of instance the same type:

class Program : child
{
    void Method()
    {
        Program p1 = new Program();
        p1.printFirstName(); // this works

        child c1 = new child();
        p1.printFirstName(); // this gives your compiler error
}

But you cannot access a protected method of an instance of a different type, even if it is a type you derived from.

See C# Reference for more details.

Upvotes: 4

Geek
Geek

Reputation: 415

In layman's terms the method marked with protected is meaning that the class itself (child) can only access the method or other class inheriting from it.

Program calling the method off 'ch' can not access it, but an instance of Program (as its inheriting child) can call the method.

Upvotes: 0

CoolBots
CoolBots

Reputation: 4869

Your code doesn't match your question - you're asking why can't Program class call protected method of it's parent (that is, child class in your example) - but your code is showing an instance of child class trying to publicly access a protected method - which fails, as intended.

This would work:

printLastName();

Or:

new Program().printLastName();

Upvotes: 0

KAMAL
KAMAL

Reputation: 158

Protected keyword means that only a type and types that derive from that type can access the member. so in this scenario you can't accesses Child.printLastName() from program Because it have two levels

Parent.printLastName() -> protected Child.printLastName() -> protected

How inheritance work when you call Child.printLastName() from program class it calls Parent.printLastName() -> Child.printLastName() But parent is not accessible that's the region it is showing compilation error.

Solution :-

You can make
Parent.printLastName() -> Internal access modifier

so Parent.printLastName() is accessible in this assembly .

namespace ConsoleApplication2 { abstract class parent { public abstract void printFirstName();

        internal virtual void printLastName()
        {
            Console.WriteLine("Watson");
        }

        public void printMiddlename()
        {
            Console.WriteLine("Jane");
        }
    }

   class child : parent
    {
        public override void printFirstName()
        {
            Console.WriteLine("Mary");
        }

        protected override void printLastName()
        {
            Console.WriteLine("Parker");
        }

        public void getMiddleName()
        {
            printMiddlename();
        }
    }


   class Program : child
    {
        static void Main(string[] args)
        {
            child ch = new child();

            ch.printFirstName();
            ch.getMiddleName();
            ch.printLastName();

            Console.Read();
        }

    }
}

Upvotes: 1

Sulli
Sulli

Reputation: 401

printLastName is protected. Check the MSDN page about access modifiers:

protected

The type or member can be accessed only by code in the same class or struct, or in a class that is derived from that class.

Upvotes: 1

bot_insane
bot_insane

Reputation: 2604

C# specification Section 1.6.2 Accessibility

Each member of a class has an associated accessibility, which controls the regions of program text that are able to access the member

public - Access not limited

protected - Access limited to this class or classes derived from this class

Protected members are accessible only in current class (where it is defined) and classes derived from it.

In another word, you can access it only by this.

Upvotes: 2

Related Questions