access supper class method with the instance hirarical base

Yadlapalli Srikanth

11y1.5kC#

Dear All,

I faced one interview question in polaris, They asked me to print the virtual method of the super class with the instance of B class. Is it possible by casting? if so please try and let me know.

class hirarical
{
public virtual void print()
{
Console.WriteLine("print virtual method");
}
public void printnorm()
{
Console.WriteLine("print virtual method");
}
}
class a : hirarical
{
public override void print()
{
Console.WriteLine("print a method");
//base.print();
}
}
class B : a
{
public override void print()
{
//need to access the virtual method of hierarical class with B instance can do casting with B instance
Console.WriteLine("print B method");

}
}

//need to access the

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes11y ago
Well, as I said at the start of my previous post, you can always do this from the B class:

var h = new hirarical();
h.print();

but, unless it was something you really had to do, this would be bad programming IMO.

I can't think of any other way to do this using a cast or otherwise. In fact, I just did a quick google and came up with this thread where the Microsoft poster, Paul Zhou, appears to be agreeing with us on this:

https://social.msdn.microsoft.com/Forums/vstudio/en-US/6a66b00d-e150-4852-abbd-2a37e7a9e4eb/how-to-call-a-virtual-method-of-an-ancestor-class-that-is-higher-than-the-base-class?forum=clr
Yadlapalli Srikanth11y ago
Hi vipul,

Thank you for the reply, I told the same to the interviewer, he was not agreed with me. Can
you please check any alternate solution is there.
Vulpes11y ago
Unless you actually create an object of the hirarical class from B, then you can't call its virtual print() method directly from B.

This is because B's base class 'a' has already overridden the print() method and so invoking base.print() from B will always call a's implementation. Casting is of no use in these scenarios either and this line would actually cause a stack overflow exception:

((hirarical)this).print();

because B's print() method would be called repeatedly.

However, if you can change 'a' as well as B you can do this:

using System;

class hirarical
{
public virtual void print()
{
Console.WriteLine("print virtual method");
}

public void printnorm()
{
Console.WriteLine("print virtual method");
}
}

class a : hirarical
{
public override void print()
{
base.print(); // calls hirarical.print()
Console.WriteLine("print a method");
}
}

class B : a
{
public override void print()
{
//need to access the virtual method of hirarical class with B instance
base.print(); // calls a.print()
Console.WriteLine("print B method");
}
}

class Program
{
static void Main()
{
B b = new B();
b.print();
Console.Readkey();
}
}

The output is:

print virtual method
print a method
print B method

I'm not sure why there's also a non-virtual printnorm() method in the hirarical class which also writes 'print virtual method' to the console unless this is a trick question and you're suppose to call that instead. To do so then, of course, a cast works as it's non-virtual:

((hirarical)this).printnorm();