p248: Calling a private constructor using a derived class

dezadez · August 26th, 2011, 12:04 PM

At the bottom of page 248, there is code for a default constructor, which is private. However, it is appended with

Code:

 : this("Default Name")

because it is stated that the constructor could be called if a new class is derived from this class.

I can't quite understand how this private constructor could in fact be called by a derived class. Could someone post an example of how a class could be derived that would use this constructor?

Thanks.

ChristianNagel · August 26th, 2011, 03:28 PM

Hi,

A private constructor cannot be called from a derived class, only from within the class itself (e.g. a static member). A protected constructor can be called from a derived class.

Hope this helps.

dezadez · August 31st, 2011, 10:50 AM

Thanks Christian.

Does this mean that the 'How It Works' at the bottom of that page (248) is wrong?

m.chenani · September 9th, 2011, 05:10 PM

that code is not related to derived class! christian's answer is related to derived class but the question is not!
in 248 page of beginning visual c# 2010 is a code that related to override constructor in one class!
dude, when we have more than one constructor in one class, can call another constructor by :this([argument of another constructor])
like this code:

Code:

class test
{
private int A;
public test(int a)
{
this.A=a;
}

public test():this(10)
{
}

}

in this code we have a class that have two constructor, first have one argument, 2nd have not any argument but we need that when the programmer create a object of our class A variable have some value, if programmer doesn't set that value,*by calling 2nd constructor) when test() has called, the test(10) is called by this(10).
good luck both!