Inheritence

sris 426

Dear all, I have one base class say BaseOne in that I have 2 methods.One method should not be override by the other method.How can i achive this. Thanks, Srinivas Mateti

The Man from U N C L E

I assume you mean that one method can be overridden and the other cannot, as you cannot override a method in the same class. Nothing can stop anyone overloading the method however. On that assumption mark the overridable method as Virtual and the not overridable one as sealed.

If you have knowledge, let others light their candles at it. Margaret Fuller (1810 - 1850) www.JacksonSoft.co.uk

Eduard Keilholz

Erhm, by 'the other mothod', do you mean method 2 in the same class? If you want the method not to be overridable from the class that ionherits your class you may want to take al look at the protected[^] keyword.

.: I love it when a plan comes together :. http://www.zonderpunt.nl

dan sh

Virtual is the keyword that makes a method overridable. Even a protected virtual method can be overidden in the derived class.

It's not necessary to be so stupid, either, but people manage it. - Christian Graus, 2009 AD

sris 426

I am extreamly sorry..one method can be override by the child class and the other method should not be override the child class... Please see the correction and sorry for the mistake. Thanks, Srinivas Mateti

dan sh

Mark the method you want to override as virtual. And do not mark the other. Like:

public virtual void OverridableMethod();
public void NonOverridableMethod();

It's not necessary to be so stupid, either, but people manage it. - Christian Graus, 2009 AD

sris 426

Thanks for the reply...so from your reply what i understood is 1) Virtual methods should be override by the child class,if the child class doest implement the virtual methods then error will shown up. 2) And only virtual methods can be override by the child class non virual methods can not be implemented by child class One more q: Can I again declare virtual method as virtual in child class??? Thanks in advance, Srinivas Mateti

dan sh

sris 426 wrote:

if the child class doest implement the virtual methods then error will shown up.

No.

sris 426 wrote:

And only virtual methods can be override by the child class non virual methods can not be implemented by child class

Correct. Although I assume you mean overridden when you say implement.

sris 426 wrote:

Can I again declare virtual method as virtual in child class???

Yes they can.

It's not necessary to be so stupid, either, but people manage it. - Christian Graus, 2009 AD

PIEBALDconsult

As others have answered, you can do that. But I wonder why not allow overriding of both methods? Is this homework?

The Man from U N C L E

To clarify: sealed - Specifies that a method cannot be overriden. abstract - Specifies that a method must be implemented in a derived class. virtual - Specifies that a member may be overriden, but does not have to be. Note that if your class includes abstract members then the class itself must also be marked as abstract. http://www.dnzone.com/go?356[^] lists all the permutations of sealed, abstract etc. for c# and vb.Net. A virtual method will still be virtual in a sub-class of a sub-class unless you mark is as override sealed in the class in the middle, which then stops classes further down the inheitance tree from overriding that method. A sub-class can always declare additional methods which may or may not be overridable in turn, as you desire.

If you have knowledge, let others light their candles at it. Margaret Fuller (1810 - 1850) www.JacksonSoft.co.uk

sris 426

Thanks for the reply... Can I use sealed for methods....? I think I can not use sealed for methods...When declared sealed for methods it gave error... PLease confirm... Thanks, Srinivas Mateti

The Man from U N C L E

As I said, if you mark a method as override sealed in the class in the middle, it then stops classes further down the inheitance tree from overriding that method. So sealed can be used on a method as shown below. secondLevelClass cannot override MyMethod when inheriting from subclasstwo, but can if it inherits from subclassone, as you will see from the error if you try to compile the code below.

public class baseclass{
	public virtual void MyMethod(){
	}
}

public class subclassOne : baseclass{
	public override void MyMethod()
	{
		base.MyMethod();
	}
}

public class subclassTwo : baseclass{
	public sealed override void MyMethod()
	{
		base.MyMethod();
	}
}


public class secondlevelClass : subclassTwo{
	public override void MyMethod()
	{
		base.MyMethod();
	}
}

If you have knowledge, let others light their candles at it. Margaret Fuller (1810 - 1850) www.JacksonSoft.co.uk

PIEBALDconsult

Yeah, that's inconsistent. Methods are sealed by default, but you can't specify it unless you're sealing an otherwise virtual method. :rolleyes:

sris 426

Thanks for the answer..now i am more clear.... Thanks, Srinivas mateti