If we inherit a class do the private variables also get inherited?

Question

I know that "Yes, the variables are inherited but cannot be accessed directly by the class interface."

What I want to know is how can we access the private variables/methods from the child class

What I am trying to say is that private members are also inherited.But how to access the same without making them protected.

You can't (well actually you can) because they're *private*. — Roger Lipscombe, May 29 '12 at 12:05
Sorry guys if I was not able to make you all understand my query. Thanks to all. — Sudhanshu Jain, May 29 '12 at 12:22

Konrad Rudolph · Answer 1 · 2016-11-02T11:27:59.327

10

I know that "Yes, the variables are inherited but cannot be accessed directly by the class interface."

So you know the answer then.

What I want to know is how can we access the private variables/methods from the child class

You can’t, that’s why they are private (rather than, say, protected). The whole intention of making them private is so that you cannot access them from anywhere, notably including child classes.

Explicitly breaking this encapsulation is almost always a sign of a broken design and shouldn’t ever be part of a normal code flow. However, there are situations in which you want to reason about some code, and in these situations it may be necessary to examine even private values. Reflection libraries allow this. Here’s a simple example using the System.Reflection capabilities:

class Widget {
    private readonly string identifier;

    public Widget(string identifier) {
        this.identifier = identifier;
    }
}

class MainClass {
    public static void Main(string[] args) {
        var widget = new Widget("my_test_widget");

        var type = widget.GetType();
        var field = type.GetField("identifier",
                                  System.Reflection.BindingFlags.Instance |
                                  System.Reflection.BindingFlags.NonPublic);

        Console.WriteLine($"{field} = {field.GetValue(widget)}");
    }
}

edited Nov 02 '16 at 11:27

answered May 29 '12 at 12:05

Konrad Rudolph

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What I am trying to say is that private members are also inherited.But how to access the same without making them protected. – Sudhanshu Jain May 29 '12 at 12:10
I answered that: you can’t access them directly. – Konrad Rudolph May 29 '12 at 12:16
But how to access them if you want to ? Ans is by using reflection !! – Naresh Ravlani Nov 01 '16 at 19:09
@NareshRavlani That’s a bad answer 99% of the time. The whole point of making something `private` is to *prevent* access. Don’t violate this, there’s almost never a reason. – Konrad Rudolph Nov 01 '16 at 21:29
1

@KonradRudolph Agree. But I was asked this question in an interview. So for me it was not about Why, it was about How. – Naresh Ravlani Nov 02 '16 at 06:17
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@NareshRavlani That’s a good reason. I’ve included a minimal example in my answer. – Konrad Rudolph Nov 02 '16 at 11:28

score 5 · Answer 2 · answered May 29 '12 at 12:06

5

Make them protected. For variables, make a protected property that the child classes then use.

answered May 29 '12 at 12:06

Steve

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+1 for protected properties. Protected contract is a contract too... It's a bad idea - to expose protected fields. – Dennis May 29 '12 at 12:07
From the question "But how to access the same without making them protected." – Matsemann May 29 '12 at 12:43
@Matsemann The question was edited after I answered. That constraint wasn't there when I answered. – Steve May 29 '12 at 12:54

score 4 · Answer 3 · edited May 23 '17 at 12:16

4

You can only access private variables/methods from a derived class using reflection. You cannot access them in a "natural" way, since the whole point of making them private is to hide them from other classes (including derived classes).

edited May 23 '17 at 12:16

Community

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answered May 29 '12 at 12:07

Heinzi

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Asif Mushtaq · Answer 4 · 2012-05-29T12:46:13.567

2

Make it protected property instead of private member.

edited May 29 '12 at 12:46

answered May 29 '12 at 12:05

Asif Mushtaq

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But no, please don’t, at least not variables. Use protected properties instead, otherwise you leak implementation details the same way as when making variables public. – Konrad Rudolph May 29 '12 at 12:06
The question is asked about how to access a variable or method only in child class. – Asif Mushtaq May 29 '12 at 12:11
1

Yes. But making variables `protected` is a *bad* solution. – Konrad Rudolph May 29 '12 at 12:16
From the question "But how to access the same without making them protected." – Matsemann May 29 '12 at 12:46

score 1 · Accepted Answer · edited May 23 '17 at 12:00

1

What I want to know is how can we access the private variables/methods from the child class ......... But how to access the same without making them protected.

You might want to try using reflection:
Here is a similar question / answer that explains how this can be done.

edited May 23 '17 at 12:00

Community

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answered May 29 '12 at 12:07

Blachshma

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Please don’t just post a link as the sole content of your answer. – Konrad Rudolph May 29 '12 at 12:08

If we inherit a class do the private variables also get inherited?

5 Answers5