new versus override

[ssg31415926]

Could someone explain the implications of the differences between using
'new' and 'override' on a member declaration, please.

I checked out MSDN but it's not exactly written for the beginner. E.g.
on Name Hiding, it starts with this: "The scope of an entity typically
encompasses more program text than the declaration space of the
entity." That whizzing sound you're hearing is it going over my head!

SSG

[Andrew Kirillov]

Hello

Suppose you have some classes:

class A
{
public A() { }

public virtual void Method1()
{
System.Diagnost ics.Debug.Write Line("A.Method1 ()");
}
public virtual void Method2()
{
System.Diagnost ics.Debug.Write Line("A.Method2 ()");
}
}

class B : A
{
public B() { }

public override void Method1()
{
System.Diagnost ics.Debug.Write Line("B.Method1 ()");
}
public new void Method2()
{
System.Diagnost ics.Debug.Write Line("B.Method2 ()");
}
}
and then:

A a = new B();
a.Method1();
a.Method2();
So, you will see in output window:
B.Method1()
A.Method2()

So, if you override something, it will be accessible if you down casting to
base class. But if you creating a new method, you can not access it after
down casting to base class.

--
With best regards,
Andrew

http://www.codeproject.com/script/pr...asp?id=1181072
"ssg3141592 6" <ne**********@g mail.com> wrote in message
news:11******** **************@ g14g2000cwa.goo glegroups.com.. .

Could someone explain the implications of the differences between using
'new' and 'override' on a member declaration, please.

I checked out MSDN but it's not exactly written for the beginner. E.g.
on Name Hiding, it starts with this: "The scope of an entity typically
encompasses more program text than the declaration space of the
entity." That whizzing sound you're hearing is it going over my head!

SSG

[Andrew Kirillov]

Hello

Suppose you have some classes:

class A
{
public A() { }

public virtual void Method1()
{
System.Diagnost ics.Debug.Write Line("A.Method1 ()");
}
public virtual void Method2()
{
System.Diagnost ics.Debug.Write Line("A.Method2 ()");
}
}

class B : A
{
public B() { }

public override void Method1()
{
System.Diagnost ics.Debug.Write Line("B.Method1 ()");
}
public new void Method2()
{
System.Diagnost ics.Debug.Write Line("B.Method2 ()");
}
}
and then:

A a = new B();
a.Method1();
a.Method2();
So, you will see in output window:
B.Method1()
A.Method2()

So, if you override something, it will be accessible if you down casting to
base class. But if you creating a new method, you can not access it after
down casting to base class.

--
With best regards,
Andrew

http://www.codeproject.com/script/pr...asp?id=1181072
"ssg3141592 6" <ne**********@g mail.com> wrote in message
news:11******** **************@ g14g2000cwa.goo glegroups.com.. .

Could someone explain the implications of the differences between using
'new' and 'override' on a member declaration, please.

I checked out MSDN but it's not exactly written for the beginner. E.g.
on Name Hiding, it starts with this: "The scope of an entity typically
encompasses more program text than the declaration space of the
entity." That whizzing sound you're hearing is it going over my head!

SSG

[shiv_koirala]

I can be wrong
Both are keywords New is for object creation
and overrides if you want to overirde a method in inheritance

Shivprasad Koirala
C# , VB.NET , SQL SERVER , ASP.NET Interview Questions
http://www.geocities.com/dotnetinterviews/

[shiv_koirala]

I can be wrong
Both are keywords New is for object creation
and overrides if you want to overirde a method in inheritance

Shivprasad Koirala
C# , VB.NET , SQL SERVER , ASP.NET Interview Questions
http://www.geocities.com/dotnetinterviews/

[GrahamJWalsh]

I'm new to C# so forgive me if my question is trivial.

In the example given by Andrew above;

" So, if you override something, it will be accessible if you down
casting to
base class. But if you creating a new method, you can not access it
after
down casting to base class. "

Don't you not mean downcasting to *derived* class?

Am I right in thinking that if you have;

A a = new B;

then you *cannot* invoke B.method2() because it's declared "new" and is
thus not accessible from an A pointer. (pointer, I think is the wrong
term here, I'm coming at this from C++).

In order to do call it, you need to do something like
B b = new B;
b.method2();

Is that correct? Again, sorry if this is c# 101, I've read the tutorial
from softsteel and am just trying to ramp up.

thanks much

Graham

[GrahamJWalsh]

I'm new to C# so forgive me if my question is trivial.

In the example given by Andrew above;

" So, if you override something, it will be accessible if you down
casting to
base class. But if you creating a new method, you can not access it
after
down casting to base class. "

Don't you not mean downcasting to *derived* class?

Am I right in thinking that if you have;

A a = new B;

then you *cannot* invoke B.method2() because it's declared "new" and is
thus not accessible from an A pointer. (pointer, I think is the wrong
term here, I'm coming at this from C++).

In order to do call it, you need to do something like
B b = new B;
b.method2();

Is that correct? Again, sorry if this is c# 101, I've read the tutorial
from softsteel and am just trying to ramp up.

thanks much

Graham

[Andrew Kirillov]

Yes, you are right. If you need B's version of Method2, you need to do

B b = new B();

b.Method2();

It's not accessible through

A a = new B();

a.Method2(); // here is call to A's version of Method2


--
With best regards,
Andrew

http://www.codeproject.com/script/pr...asp?id=1181072
<Gr**********@g mail.com> wrote in message
news:11******** **************@ g14g2000cwa.goo glegroups.com.. .

I'm new to C# so forgive me if my question is trivial.

In the example given by Andrew above;

" So, if you override something, it will be accessible if you down
casting to
base class. But if you creating a new method, you can not access it
after
down casting to base class. "

Don't you not mean downcasting to *derived* class?

Am I right in thinking that if you have;

A a = new B;

then you *cannot* invoke B.method2() because it's declared "new" and is
thus not accessible from an A pointer. (pointer, I think is the wrong
term here, I'm coming at this from C++).

In order to do call it, you need to do something like
B b = new B;
b.method2();

Is that correct? Again, sorry if this is c# 101, I've read the tutorial
from softsteel and am just trying to ramp up.

thanks much

Graham

[Andrew Kirillov]

Yes, you are right. If you need B's version of Method2, you need to do

B b = new B();

b.Method2();

It's not accessible through

A a = new B();

a.Method2(); // here is call to A's version of Method2


--
With best regards,
Andrew

http://www.codeproject.com/script/pr...asp?id=1181072
<Gr**********@g mail.com> wrote in message
news:11******** **************@ g14g2000cwa.goo glegroups.com.. .

I'm new to C# so forgive me if my question is trivial.

In the example given by Andrew above;

" So, if you override something, it will be accessible if you down
casting to
base class. But if you creating a new method, you can not access it
after
down casting to base class. "

Don't you not mean downcasting to *derived* class?

Am I right in thinking that if you have;

A a = new B;

then you *cannot* invoke B.method2() because it's declared "new" and is
thus not accessible from an A pointer. (pointer, I think is the wrong
term here, I'm coming at this from C++).

In order to do call it, you need to do something like
B b = new B;
b.method2();

Is that correct? Again, sorry if this is c# 101, I've read the tutorial
from softsteel and am just trying to ramp up.

thanks much

Graham

[Andrew Kirillov]

Yes, a little bit wrong.

New is not only for object creation. It's also a modifier to class
methods/properties declaration.


--
With best regards,
Andrew

http://www.codeproject.com/script/pr...asp?id=1181072
<sh**********@y ahoo.com> wrote in message
news:11******** **************@ g49g2000cwa.goo glegroups.com.. .

I can be wrong
Both are keywords New is for object creation
and overrides if you want to overirde a method in inheritance

Shivprasad Koirala
C# , VB.NET , SQL SERVER , ASP.NET Interview Questions
http://www.geocities.com/dotnetinterviews/