arraylist copy

[Sam]

Hi,

I have the following code :

Dim rNodeList As New ArrayList
Dim rNodeListNew As New ArrayList

For iCntr As Integer = 0 To tvRelations.Nod es.Count - 1
rNodeList.Add(t vRelations.Node s(iCntr).Text)
Next

rNodeListNew = rNodeList
rNodeList.Remov eAt(2)

after I've filled rNodeList, it contains 8 elements.
So does rNodeListNew

But when I remove the element 2 of rNodeList, it is also removed in
rNodeListNew. Why ? Do they both point to the same memory location ?
How can I prevent that in vb ?

Thx

[Herfried K. Wagner [MVP]]

"J L" <jo**@marymonte .com> schrieb:

What does "shallow" and "deep" copy mean?

An insight into cloning objects in .NET
<URL:http://www.codeproject .com/dotnet/Clone.asp>

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

[Cor Ligthert]

"Joseph

Thanks! Then what is the difference between CopyTo and Clone? MSDN
mentioned that clone creates a shallow copy and copyto creates a deep
copy? Thanks again!

A clone makes a copy of the arraylist. While an array is a reference type,
are only the references copied. Any change in a shadow will affect on the
other one as well. Except when it is by instance the removing or adding of a
reference (row), than they grew apart.

A copyto makes a copy of the values in a one dimensional array. Where when
it are objects it is in fact again a shadow of course.

A deep copy makes new copy of all the values and creates a new arraylist
arround those. For that I have never seen a method in Net. You have to do it
yourself. (In my opinion can that be complicated when it is by instance a
jagged array).

I hope this gives some idea's

Cor

[Cor Ligthert]

JL

See my message to Joseph

Cor

[Dennis]

If I am reading the articles correctly then if an object implements the
Icloneable interfact and it is cloned, then for all the value types the value
is copied to the new object and for all the reference types, only the
reference(point ers) are copied. So what is gained? If I have an arraylist
of value type objects then the .Clone Method will copy the values to a new
arraylist but if the arraylist objects are reference types then only the
reference is copied to the new arraylist. Then when I change a value type in
the new arraylist, the original arraylist is not changed but If I change a
reference type in the new arrraylist, then the original arraylist will also
reflect that change since they both point to the same instance of the object.
Is all this correct?

"Herfried K. Wagner [MVP]" wrote:

"J L" <jo**@marymonte .com> schrieb:

What does "shallow" and "deep" copy mean?

An insight into cloning objects in .NET
<URL:http://www.codeproject .com/dotnet/Clone.asp>

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

[J L]

Thanks Cor, that does help.

John

On Sat, 9 Apr 2005 09:21:15 +0200, "Cor Ligthert"
<no************ @planet.nl> wrote:

"Joseph

Thanks! Then what is the difference between CopyTo and Clone? MSDN
mentioned that clone creates a shallow copy and copyto creates a deep
copy? Thanks again!

A clone makes a copy of the arraylist. While an array is a reference type,
are only the references copied. Any change in a shadow will affect on the
other one as well. Except when it is by instance the removing or adding of a
reference (row), than they grew apart.

A copyto makes a copy of the values in a one dimensional array. Where when
it are objects it is in fact again a shadow of course.

A deep copy makes new copy of all the values and creates a new arraylist
arround those. For that I have never seen a method in Net. You have to do it
yourself. (In my opinion can that be complicated when it is by instance a
jagged array).

I hope this gives some idea's

Cor

[Joseph MCAD]

April 9, 2005

Thanks for everybody's replies!

Joseph MCAD
"Cor Ligthert" <no************ @planet.nl> wrote in message
news:uc******** ******@tk2msftn gp13.phx.gbl...

"Joseph

Thanks! Then what is the difference between CopyTo and Clone? MSDN
mentioned that clone creates a shallow copy and copyto creates a deep
copy? Thanks again!

A clone makes a copy of the arraylist. While an array is a reference type,
are only the references copied. Any change in a shadow will affect on the
other one as well. Except when it is by instance the removing or adding of
a reference (row), than they grew apart.

A copyto makes a copy of the values in a one dimensional array. Where when
it are objects it is in fact again a shadow of course.

A deep copy makes new copy of all the values and creates a new arraylist
arround those. For that I have never seen a method in Net. You have to do
it yourself. (In my opinion can that be complicated when it is by instance
a jagged array).

I hope this gives some idea's

Cor