Collection/list problem

[Clive Lumb]

Hi,

I'm having a problem while adding objects to a collection. (VB.net 2005)
I am reading data in from a file to a temporary variable (eg MyClass) and
then adding it to a collection.
When I then enumerate the collection, all the entries are equal to the last
one added.
The same thing happens with lists and with a generic list(of type).
Obviously the collection or list is storing a reference to the variable,
rather than the values - hence all the items refer to the same variable.

I am probably missing something really basic - please be patient :-)

Many TIA

example:

Public Class MyThing
name as String
Value as integer
end class

Dim MyClass as New MyThing
Dim MyCollection as New Collection

'open file
'do
' read in name, value
MyClass.name=Na meFromFile
MyClass.value=V alueFromFile
MyCollection.Ad d(MyClass)
'loop to end of file
'close file

[Patrice]

Re: Collection/list problem

You need to add MyClass=New MyThing inside the loop.

Here you always adding the same object to the collection. Even once the
object is added to the collection you can change the object properties
(basically an object is a pointer actual data).

I would recommend reading once the language specification to clear out the
basics...

--
Patrice

"Clive Lumb" <clumb2@gratuit _en_anglais.fr. invalida écrit dans le message
de groupe de discussion : 488839a0$0$2131 2$426a74cc@news .free.fr...

Hi,
>
I'm having a problem while adding objects to a collection. (VB.net 2005)
I am reading data in from a file to a temporary variable (eg MyClass) and
then adding it to a collection.
When I then enumerate the collection, all the entries are equal to the
last
one added.
The same thing happens with lists and with a generic list(of type).
Obviously the collection or list is storing a reference to the variable,
rather than the values - hence all the items refer to the same variable.
>
I am probably missing something really basic - please be patient :-)
>
Many TIA
>
example:
>
Public Class MyThing
name as String
Value as integer
end class
>
Dim MyClass as New MyThing
Dim MyCollection as New Collection
>
'open file
'do
' read in name, value
MyClass.name=Na meFromFile
MyClass.value=V alueFromFile
MyCollection.Ad d(MyClass)
'loop to end of file
'close file
>
>
>

[Clive Lumb]

Re: Collection/list problem

Hello Patrice

Thanks for the speedy reply!
I shall try that immediately

"Patrice" <http://www.chez.com/scribe/a écrit dans le message de news:
7A8AF0C2-88AC-4B3D-9FBC-24835CAF46F3@mi crosoft.com...

You need to add MyClass=New MyThing inside the loop.
>
Here you always adding the same object to the collection. Even once the
object is added to the collection you can change the object properties
(basically an object is a pointer actual data).
>
I would recommend reading once the language specification to clear out the
basics...
>
--
Patrice
>
"Clive Lumb" <clumb2@gratuit _en_anglais.fr. invalida écrit dans le
message de groupe de discussion :
488839a0$0$2131 2$426a74cc@news .free.fr...

>Hi,
>>
>I'm having a problem while adding objects to a collection. (VB.net 2005)
>I am reading data in from a file to a temporary variable (eg MyClass) and
>then adding it to a collection.
>When I then enumerate the collection, all the entries are equal to the
>last
>one added.
>The same thing happens with lists and with a generic list(of type).
>Obviously the collection or list is storing a reference to the variable,
>rather than the values - hence all the items refer to the same variable.
>>
>I am probably missing something really basic - please be patient :-)
>>
>Many TIA
>>
>example:
>>
>Public Class MyThing
> name as String
> Value as integer
>end class
>>
>Dim MyClass as New MyThing
>Dim MyCollection as New Collection
>>
>'open file
>'do
> ' read in name, value
> MyClass.name=Na meFromFile
> MyClass.value=V alueFromFile
> MyCollection.Ad d(MyClass)
>'loop to end of file
>'close file
>>
>>
>>

>

[Clive Lumb]

Re: Collection/list problem

Yay! it works!

I would recommend reading once the language specification to clear out the
basics...
>

Unfortunately I have the French version which is dire, for example it says
that objects in a collection *should* not be of the same type (instead of
*need* not).



"Patrice" <http://www.chez.com/scribe/a écrit dans le message de news:
7A8AF0C2-88AC-4B3D-9FBC-24835CAF46F3@mi crosoft.com...

You need to add MyClass=New MyThing inside the loop.
>
Here you always adding the same object to the collection. Even once the
object is added to the collection you can change the object properties
(basically an object is a pointer actual data).
>
I would recommend reading once the language specification to clear out the
basics...
>
--
Patrice
>
"Clive Lumb" <clumb2@gratuit _en_anglais.fr. invalida écrit dans le
message de groupe de discussion :
488839a0$0$2131 2$426a74cc@news .free.fr...

>Hi,
>>
>I'm having a problem while adding objects to a collection. (VB.net 2005)
>I am reading data in from a file to a temporary variable (eg MyClass) and
>then adding it to a collection.
>When I then enumerate the collection, all the entries are equal to the
>last
>one added.
>The same thing happens with lists and with a generic list(of type).
>Obviously the collection or list is storing a reference to the variable,
>rather than the values - hence all the items refer to the same variable.
>>
>I am probably missing something really basic - please be patient :-)
>>
>Many TIA
>>
>example:
>>
>Public Class MyThing
> name as String
> Value as integer
>end class
>>
>Dim MyClass as New MyThing
>Dim MyCollection as New Collection
>>
>'open file
>'do
> ' read in name, value
> MyClass.name=Na meFromFile
> MyClass.value=V alueFromFile
> MyCollection.Ad d(MyClass)
>'loop to end of file
>'close file
>>
>>
>>

>

[Lev Blaivas]

Re: Collection/list problem

On Jul 24, 11:54 am, "Clive Lumb"
<clumb2@gratuit _en_anglais.fr. invalidwrote:

Yay! it works!
>

I would recommend reading once the language specification to clear out the
basics...

>
Unfortunately I have the French version which is dire, for example it says
that objects in a collection *should* not be of the same type (instead of
*need* not).
>
"Patrice" <http://www.chez.com/scribe/a écrit dans le message de news:
7A8AF0C2-88AC-4B3D-9FBC-24835CAF4...@mi crosoft.com...
>

You need to add MyClass=New MyThing inside the loop.

>

Here you always adding the same object to the collection. Even once the
object is added to the collection you can change the object properties
(basically an object is a pointer actual data).

>

I would recommend reading once the language specification to clear out the
basics...

>

--
Patrice

>

"Clive Lumb" <clumb2@gratuit _en_anglais.fr. invalida écrit dans le
message de groupe de discussion :
488839a0$0$2131 2$426a7...@news .free.fr...

Hi,

>

I'm having a problem while adding objects to a collection. (VB.net 2005)
I am reading data in from a file to a temporary variable (eg MyClass) and
then adding it to a collection.
When I then enumerate the collection, all the entries are equal to the
last
one added.
The same thing happens with lists and with a generic list(of  type).
Obviously the collection or list is storing a reference to the variable,
rather than the values - hence all the items refer to the same variable.

>

I am probably missing something really basic - please be patient :-)

>

Many TIA

>

example:

>

Public Class MyThing
   name as String
   Value as integer
end class

>

Dim MyClass as New MyThing
Dim MyCollection as New Collection

>

'open file
'do
   ' read in name, value
   MyClass.name=Na meFromFile
   MyClass.value=V alueFromFile
   MyCollection.Ad d(MyClass)
'loop to end of file
'close file

Here is a great article about reference and value types;

http://www.ondotnet.com/lpt/a/2789

explains in detail the difference between value and reference types