C#, Inheritance and casting..!!

Question

1.00/5 (1 vote)

See more:

C#

using System;
using System.Collections.Generic;
using System.Text;
namespace ConsoleApplication1
{
    class A
    {
    }
    class B:A
    {
    }
    class c
    {
        static void Main(string[] args)
        {
            B obj1 = new A();
        }
    }
}

Will it execute ??..and if not.. can anyone give me the exact answer ???

Posted 16-Sep-10 1:16am

arindam2010

Updated 16-Sep-10 1:28am

#realJSOP

v2

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Alex@UEA · Accepted Answer · 2010-09-16T01:33:00

Solution 3

If B is a subclass of A then I think

A obj1 = new B() is fine but not vice versa

you can use a superclass to ref a subclass but not a subclass to ref a superclass

you might be able to cast it though

Posted 16-Sep-10 1:33am

Alex@UEA

Updated 16-Sep-10 1:34am

v2

Comments

arindam2010 16-Sep-10 7:50am

Reason for my vote of 5
Automatic vote of 5 for accepting answer.

Al-Farooque Shubho · Accepted Answer · 2010-09-16T01:27:00

Solution 1

No, it won't execute.

If you write A obj1 = new B();, it will execute.

Why?

Because, A is the base class and B is the class that extends B. So, according to OOP, B "is a" A as A is in upper position in the inheritance hirarchy. So, it is always possible to assign an object of B to a reference of A. But, the opposite wouln't execute.

However, If you cast the object as follows, then it will compile, but, won't execute:

B obj1 = (B)new A();

Posted 16-Sep-10 1:27am

Al-Farooque Shubho

Updated 16-Sep-10 4:16am

v2

Comments

Kubajzz 16-Sep-10 7:33am

Actually your last sentence is not exactly true. It will compile, but it will not execute, because an exception will be thrown at runtime... Good answer anyway, have my 4.

Hiren solanki 16-Sep-10 7:34am

Good Answer

Dalek Dave 16-Sep-10 7:37am

Good Call.

arindam2010 16-Sep-10 7:50am

Reason for my vote of 5
Automatic vote of 5 for accepting answer.

Al-Farooque Shubho 16-Sep-10 10:11am

Good catch Kubajzz. Yes, I actually wanted to mean "Compile" not "execute". Slip of pen :) (Updated the answer accordingly).