Problem with inheritance in C#.

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1.00/5 (1 vote)

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I have a little problem with C# inheritance. It's easy but I cant figure it out!
Suppose I have a parent class and a child class(child:parent).
I just want to know if we define (child = new parent) can we access to child properties? Because I tried it but I couldn't do that, by the way i think it should work..

Here is a example code:

C#

public class Parent
    {
        private int _Parent1;

        public int Parent1
        {
            get { return _Parent1; }
            set { _Parent1 = value; }
        }   
    }

public class Child1 : Parent
    {
        private int _Child1Prop;

        public int Child1Prop
        {
            get { return _Child1Prop; }
            set { _Child1Prop = value; }
        }
    }

suppose

C#

Parent test = new Child1();

Is this possible:?

C#

test.Child1Prop = some value;

Posted 22-Dec-11 11:28am

alizadeh91

Updated 23-Dec-11 0:54am

v3

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[no name] 23-Dec-11 6:14am

alizadeh91--> plz dig deep in CPallini's answer. It makes scene.

6 solutions

Solution 5

C#

child1 test = new Parent;

simply this isn't possible.

"your solution works but i dont want to use casting!!!"

There is no way to do something like that with or without casting, it's not allowed.

You can do this:

C#

public class Child1 : Parent
{
    public static implicit operator Child2(Child1 ch2)
    {
        return new Child2();
    }
}

public class Child2 : Child1
{
    Child2 ch2 = new Child1();
}

but not in this case:

C#

child1 test = new Parent;

Posted 23-Dec-11 0:00am

Drazen Pupovac

Comments

RaviRanjanKr 23-Dec-11 15:43pm

My 5+

Drazen Pupovac 23-Dec-11 16:49pm

Thank you

Solution 3

Friends thanks for answering but it's completely possible to write:

child1 test = new Parent;

i just wanna know after this declaration can i access to child1 properties???

Posted 22-Dec-11 20:53pm

alizadeh91

v2

Comments

CPallini 23-Dec-11 4:15am

C'mon: if you ever instantiate a 'Parent' class (and the compiler won't allow it) how could you access Child1 properties (they simply don't exist)?

alizadeh91 23-Dec-11 11:19am

Thats right CPallini i'm really sorry that was a mistake i meant Parent test = new Child1();
anyway my problem still exists!!!!

RaviRanjanKr 23-Dec-11 15:44pm

A suggestion :- you can use Have a question or Comment button to drop your message and to get Immediate response instead of posting as answer.

Solution 4

Come on guys.. :( answer it .. it's really easy!

Posted 22-Dec-11 21:06pm

alizadeh91

Comments

RaviRanjanKr 23-Dec-11 15:44pm

A suggestion :- you can use Have a question or Comment button to drop your message and to get Immediate response instead of posting as answer.

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CPallini · Accepted Answer · 2011-12-22T12:23:00

Solution 1

You cannot write

C#

Child=new Parent;

The compiler would complain.

[updated]

OK, you rephrased the question, now:

C#

Parent test = new Child1();
test.Child1Prop = some value;

is not possible.

However, for instance:

C#

Parent parent = new Child1();
(parent as Child1).Child1Prop = 5;

would work fine.

[/update]

Posted 22-Dec-11 12:23pm

CPallini

Updated 23-Dec-11 1:45am

v3

Comments

alizadeh91 23-Dec-11 2:51am

Actually i can!! try it.. that's way of object oriented programming!

CPallini 23-Dec-11 4:07am

Nope: object oriented programming goes into the opposite direction:
Parent parent = new Child1();
Did you try to compile it?

[no name] 23-Dec-11 6:14am

5!

CPallini 23-Dec-11 6:17am

Thanks.

alizadeh91 23-Dec-11 6:38am

actually i meant that :D Yea that was a mistake suppose: Parent parent = new Child1();
thanks guys :) anyway can i do that???

alizadeh91 23-Dec-11 6:54am

I've revised my question! :)

RaisKazi 23-Dec-11 8:43am

My 5.

CPallini 23-Dec-11 8:55am

Thank you.

Drazen Pupovac · Accepted Answer · 2011-12-22T12:38:00

This isn't possible:

C#

child1 test = new Parent;

You can't cast base to the child object. From my experience this isn't possible. You can implement constructor in Child1 class like this:

C#

public Child1(Parent parent)
{
   _Child1Prop = 2;
}

BUT you can do something like this:

C#

    public class Parent
    {
    }

    public class Child1 : Parent
    {
    }

    public class Child2 : Child1
    {
    }

    public class Child3 : Child2
    {
    }

//-------------- somewhere in Main -------
    Child3 ch3 = new Child3();
    Child1 ch1 = (Child1)ch3;
    Child2 ch2 = (Child2)ch1;

I hope you're asked this.

Estys · Accepted Answer · 2011-12-23T01:26:00

Suppose you have a class Child2 as well :

public class Child2 : Parent

The following shows what is possible and what is going to happen :

C#

Parent test = new Child1();  // permitted
Child1 test1 = test as Child1; // permitted
Child1 test2 = (Child1)test; // permitted

((Child1)test).Child1Prop = 5; // explicit cast of test
test1.Child1Prop = 5;
test2.Child1Prop = 5;

Parent test3 = new Child2();  // permitted
Child1 test4 = test3 as Child1; // test4 will be null, cannot be cast to Child1
Child1 test5 = (Child1)test3; // runtime exception, test3 cannot be cast to Child1

// if somehow no exception has occurred 
((Child1)test3).Child1Prop = 5; // runtime exception, test3 cannot be cast to Child1
test4.Child1Prop = 5; // null pointer exception on test4
test5.Child1Prop = 5; // if test3 magically had been cast to Child1, no such method or property exception

Cheers

Problem with inheritance in C#.

6 solutions

Solution 1

Solution 2

Solution 5

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Solution 3

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