ArrayList Help

[GrandpaB]

While writing this plea for help, I think I solved my
dilemma, but I don't know why the problem solving
statement is necessary. The inspiration for the
statement came from an undocumented VB example I found on
the web. I would be most appreciative if someone could
explain why this statement is necessary and what does it
do:

MyArt = New Art

Early in the code, ArtList, MyArt & AddNew had been
declared with the following statements:

Public ArtList as New ArrayList
Public MyArt as New Art
Public AddNew as Boolean

I am creating a Windows application which uses an
ArrayList to contain a small amount of data. ArtList, is
an instance of an ArrayList that will contain multiple
(up to 200) Art objects. MyArt is an instance of the Art
object. In the application I want to add, delete and
edit the individual Art objects in ArtList. I am
serializing and deserializing the ArrayList and using a
FileStream to read and write to the hard drive. This is
the code in question, and the mystery statement is
commented with ******

Private Sub btnNew_Click(By Val sender As System.Object, _
ByVal e As System.EventArg s) Handles btnNew.Click

ClearForm() 'A sub to clear the Form's textboxes
AddNew = True
End Sub

Private Sub btnAdd_Click(By Val sender As System.Object, _
ByVal e As System.EventArg s) Handles btnAdd.Click

Dim Msg1 As String = "Do you want to ADD this new
Object?"
Dim Msg2 As String = "Update Art"
Dim Ans As MsgBoxResult
If FormChanged() And AddNew Then
Ans = MsgBox(Msg1, MsgBoxStyle.Yes No, Msg2)
If Ans = MsgBoxResult.Ye s Then
MyArt = New Art '??? ********* ???
Form2MyArt() 'Move textbox entries to MyArt
ArtList.Add(MyA rt)
SaveFile() 'Serialize ArtList & write
FileStream
End If
End if
End Sub

[Cor Ligthert]

GrandpaB

A try to answer as short as possible.

Public MyArt as New Art
Creates a new object from the class Art and does the sub New in that class

MyArt as New art
Creates a new object from the class Art and does the sub New in that class
The previous MyArt looses his reference and will therefore be deleted by the
Garbage Collector (GC) when that start doing its job.

And not important, an object is forever created on the managed heap.

I hope this helps?

Cor

"GrandpaB" <an*******@disc ussions.microso ft.com>

While writing this plea for help, I think I solved my
dilemma, but I don't know why the problem solving
statement is necessary. The inspiration for the
statement came from an undocumented VB example I found on
the web. I would be most appreciative if someone could
explain why this statement is necessary and what does it
do:

MyArt = New Art

Early in the code, ArtList, MyArt & AddNew had been
declared with the following statements:

Public ArtList as New ArrayList
Public MyArt as New Art
Public AddNew as Boolean

I am creating a Windows application which uses an
ArrayList to contain a small amount of data. ArtList, is
an instance of an ArrayList that will contain multiple
(up to 200) Art objects. MyArt is an instance of the Art
object. In the application I want to add, delete and
edit the individual Art objects in ArtList. I am
serializing and deserializing the ArrayList and using a
FileStream to read and write to the hard drive. This is
the code in question, and the mystery statement is
commented with ******

Private Sub btnNew_Click(By Val sender As System.Object, _
ByVal e As System.EventArg s) Handles btnNew.Click

ClearForm() 'A sub to clear the Form's textboxes
AddNew = True
End Sub

Private Sub btnAdd_Click(By Val sender As System.Object, _
ByVal e As System.EventArg s) Handles btnAdd.Click

Dim Msg1 As String = "Do you want to ADD this new
Object?"
Dim Msg2 As String = "Update Art"
Dim Ans As MsgBoxResult
If FormChanged() And AddNew Then
Ans = MsgBox(Msg1, MsgBoxStyle.Yes No, Msg2)
If Ans = MsgBoxResult.Ye s Then
MyArt = New Art '??? ********* ???
Form2MyArt() 'Move textbox entries to MyArt
ArtList.Add(MyA rt)
SaveFile() 'Serialize ArtList & write
FileStream
End If
End if
End Sub

Cor,

Thanks for your assistance; yes, I think that I'm
starting to gain some insight to improve my
understanding, but I still have a puzzlement.

Let me reitterate to see if I understand. My original
statement:

Public MyArt as New Art

created MyArt as a new Art object. With this object I
was able run the subroutine:

Sub DisplayArt(ByVa l Index As Integer)
'Transfer the ArtList(Index) to MyArt and then to
the form
MyArt = ArtList(Index)
MyArt2Form()
End Sub

and the statements:

Form2MyArt()
ArtList(Index)= MyArt

to sucessfully edit the various objects in ArtList, but
when I wanted to add a item to ArtList I had to include
the statement:

MyArt = New Art

So why could I use the original MyArt to edit various
items in ArtList, but when I wanted to add an item to
ArtList I needed reinitialize MyArt using the following
statements:

MyArt = New Art '??? **** ???
Form2MyArt
ArtList.Add(MyA rt)

Thanks in advance, GrandpaB

-----Original Message-----
GrandpaB

A try to answer as short as possible.

Public MyArt as New Art
Creates a new object from the class Art and does the sub New in that class
MyArt as New art
Creates a new object from the class Art and does the sub New in that classThe previous MyArt looses his reference and will therefore be deleted by theGarbage Collector (GC) when that start doing its job.

And not important, an object is forever created on the managed heap.
I hope this helps?

Cor

"GrandpaB" <an*******@disc ussions.microso ft.com>

While writing this plea for help, I think I solved my
dilemma, but I don't know why the problem solving
statement is necessary. The inspiration for the
statement came from an undocumented VB example I found on the web. I would be most appreciative if someone could
explain why this statement is necessary and what does it do:

MyArt = New Art

Early in the code, ArtList, MyArt & AddNew had been
declared with the following statements:

Public ArtList as New ArrayList
Public MyArt as New Art
Public AddNew as Boolean

I am creating a Windows application which uses an
ArrayList to contain a small amount of data. ArtList, is an instance of an ArrayList that will contain multiple
(up to 200) Art objects. MyArt is an instance of the Art object. In the application I want to add, delete and
edit the individual Art objects in ArtList. I am
serializing and deserializing the ArrayList and using a
FileStream to read and write to the hard drive. This is
the code in question, and the mystery statement is
commented with ******

Private Sub btnNew_Click(By Val sender As System.Object, _ ByVal e As System.EventArg s) Handles btnNew.Click

ClearForm() 'A sub to clear the Form's textboxes
AddNew = True
End Sub

Private Sub btnAdd_Click(By Val sender As System.Object, _ ByVal e As System.EventArg s) Handles btnAdd.Click

Dim Msg1 As String = "Do you want to ADD this new
Object?"
Dim Msg2 As String = "Update Art"
Dim Ans As MsgBoxResult
If FormChanged() And AddNew Then
Ans = MsgBox(Msg1, MsgBoxStyle.Yes No, Msg2)
If Ans = MsgBoxResult.Ye s Then
MyArt = New Art '??? ********* ???
Form2MyArt() 'Move textbox entries to MyArt
ArtList.Add(MyA rt)
SaveFile() 'Serialize ArtList & write
FileStream
End If
End if
End Sub

.

[Cor Ligthert]

Grandpa

I see it,

When you add that myArt to the arraylist than there is a reference from the
arraylist to it.

Better, it are everytime objects in the arraylist which are referenced and
stay referenced until they are removed from the arraylist or the arraylist
does not exist anymore.

I did not completly look at your code. However probably I would not do it
that way as you do it and use instead of
MyArt = New Art '??? ********* ???

Dim myArt as New art '??? ********* ???

For as far as I can see the code, do I as well not see sense for that
Public MyArt as New Art.

You only need to create objects for in your arraylist from the type of Art.

I hope this helps?

Cor
<an*******@disc ussions.microso ft.com>

Cor,

Thanks for your assistance; yes, I think that I'm
starting to gain some insight to improve my
understanding, but I still have a puzzlement.

Let me reitterate to see if I understand. My original
statement:

Public MyArt as New Art

created MyArt as a new Art object. With this object I
was able run the subroutine:

Sub DisplayArt(ByVa l Index As Integer)
'Transfer the ArtList(Index) to MyArt and then to
the form
MyArt = ArtList(Index)
MyArt2Form()
End Sub

and the statements:

Form2MyArt()
ArtList(Index)= MyArt

to sucessfully edit the various objects in ArtList, but
when I wanted to add a item to ArtList I had to include
the statement:

MyArt = New Art

So why could I use the original MyArt to edit various
items in ArtList, but when I wanted to add an item to
ArtList I needed reinitialize MyArt using the following
statements:

MyArt = New Art '??? **** ???
Form2MyArt
ArtList.Add(MyA rt)

Thanks in advance, GrandpaB

-----Original Message-----
GrandpaB

A try to answer as short as possible.

Public MyArt as New Art
Creates a new object from the class Art and does the sub

New in that class

MyArt as New art
Creates a new object from the class Art and does the sub

New in that class

The previous MyArt looses his reference and will

therefore be deleted by the

Garbage Collector (GC) when that start doing its job.

And not important, an object is forever created on the

managed heap.

I hope this helps?

Cor

"GrandpaB" <an*******@disc ussions.microso ft.com>

While writing this plea for help, I think I solved my
dilemma, but I don't know why the problem solving
statement is necessary. The inspiration for the
statement came from an undocumented VB example I found on the web. I would be most appreciative if someone could
explain why this statement is necessary and what does it do:

MyArt = New Art

Early in the code, ArtList, MyArt & AddNew had been
declared with the following statements:

Public ArtList as New ArrayList
Public MyArt as New Art
Public AddNew as Boolean

I am creating a Windows application which uses an
ArrayList to contain a small amount of data. ArtList, is an instance of an ArrayList that will contain multiple
(up to 200) Art objects. MyArt is an instance of the Art object. In the application I want to add, delete and
edit the individual Art objects in ArtList. I am
serializing and deserializing the ArrayList and using a
FileStream to read and write to the hard drive. This is
the code in question, and the mystery statement is
commented with ******

Private Sub btnNew_Click(By Val sender As System.Object, _ ByVal e As System.EventArg s) Handles btnNew.Click

ClearForm() 'A sub to clear the Form's textboxes
AddNew = True
End Sub

Private Sub btnAdd_Click(By Val sender As System.Object, _ ByVal e As System.EventArg s) Handles btnAdd.Click

Dim Msg1 As String = "Do you want to ADD this new
Object?"
Dim Msg2 As String = "Update Art"
Dim Ans As MsgBoxResult
If FormChanged() And AddNew Then
Ans = MsgBox(Msg1, MsgBoxStyle.Yes No, Msg2)
If Ans = MsgBoxResult.Ye s Then
MyArt = New Art '??? ********* ???
Form2MyArt() 'Move textbox entries to MyArt
ArtList.Add(MyA rt)
SaveFile() 'Serialize ArtList & write
FileStream
End If
End if
End Sub

.

[GrandpaB]

Cor,

Thanks again for the followup. I guess that my question
boils down to: Why can I transfer existing objects, back
and forth, between AtrList(Index) and MyArt after
declaring ArtList and MyArt with:

Public ArtList as New ArrayList
Public MyArt as New Art

but when I want to add a new object to ArtList,
ArtList.Add(MyA rt), I must reinitialize MyArt with:

MyArt = New Art

or, as you suggest, with

Dim MyArt as New Art

The code works and that is my first concern, but I am
attempting to deepen my understanding of VB.

Once again thanks, GrandpaB

-----Original Message-----
Grandpa

I see it,

When you add that myArt to the arraylist than there is a reference from thearraylist to it.

Better, it are everytime objects in the arraylist which are referenced andstay referenced until they are removed from the arraylist or the arraylistdoes not exist anymore.

I did not completly look at your code. However probably I would not do itthat way as you do it and use instead of
MyArt = New Art '??? ********* ???

Dim myArt as New art '??? ********* ???

For as far as I can see the code, do I as well not see sense for thatPublic MyArt as New Art.

You only need to create objects for in your arraylist from the type of Art.
I hope this helps?

Cor
<an*******@dis cussions.micros oft.com>

Cor,

Thanks for your assistance; yes, I think that I'm
starting to gain some insight to improve my
understanding, but I still have a puzzlement.

Let me reitterate to see if I understand. My original
statement:

Public MyArt as New Art

created MyArt as a new Art object. With this object I
was able run the subroutine:

Sub DisplayArt(ByVa l Index As Integer)
'Transfer the ArtList(Index) to MyArt and then to the form
MyArt = ArtList(Index)
MyArt2Form()
End Sub

and the statements:

Form2MyArt()
ArtList(Index)= MyArt

to sucessfully edit the various objects in ArtList, but
when I wanted to add a item to ArtList I had to include
the statement:

MyArt = New Art

So why could I use the original MyArt to edit various
items in ArtList, but when I wanted to add an item to
ArtList I needed reinitialize MyArt using the following
statements:

MyArt = New Art '??? **** ???
Form2MyArt
ArtList.Add(MyA rt)

Thanks in advance, GrandpaB

-----Original Message-----
GrandpaB

A try to answer as short as possible.

Public MyArt as New Art
Creates a new object from the class Art and does the sub

New in that class

MyArt as New art
Creates a new object from the class Art and does the

sub New in that class

The previous MyArt looses his reference and will

therefore be deleted by the

Garbage Collector (GC) when that start doing its job.

And not important, an object is forever created on the

managed heap.

I hope this helps?

Cor

"GrandpaB" <an*******@disc ussions.microso ft.com>

While writing this plea for help, I think I solved my
dilemma, but I don't know why the problem solving
statement is necessary. The inspiration for the
statement came from an undocumented VB example I

found on

the web. I would be most appreciative if someone

could explain why this statement is necessary and what does

it

do:

MyArt = New Art

Early in the code, ArtList, MyArt & AddNew had been
declared with the following statements:

Public ArtList as New ArrayList
Public MyArt as New Art
Public AddNew as Boolean

I am creating a Windows application which uses an
ArrayList to contain a small amount of data. ArtList, is

an instance of an ArrayList that will contain

multiple (up to 200) Art objects. MyArt is an instance of the

Art

object. In the application I want to add, delete and
edit the individual Art objects in ArtList. I am
serializing and deserializing the ArrayList and using a FileStream to read and write to the hard drive. This is the code in question, and the mystery statement is
commented with ******

Private Sub btnNew_Click(By Val sender As

System.Object, _

ByVal e As System.EventArg s) Handles btnNew.Click

ClearForm() 'A sub to clear the Form's textboxes
AddNew = True
End Sub

Private Sub btnAdd_Click(By Val sender As

System.Object, _

ByVal e As System.EventArg s) Handles btnAdd.Click

Dim Msg1 As String = "Do you want to ADD this new
Object?"
Dim Msg2 As String = "Update Art"
Dim Ans As MsgBoxResult
If FormChanged() And AddNew Then
Ans = MsgBox(Msg1, MsgBoxStyle.Yes No, Msg2)
If Ans = MsgBoxResult.Ye s Then
MyArt = New Art '??? ********* ???
Form2MyArt() 'Move textbox entries to MyArt ArtList.Add(MyA rt)
SaveFile() 'Serialize ArtList & write
FileStream
End If
End if
End Sub

.

.

[Larry Serflaten]

"GrandpaB" <an*******@disc ussions.microso ft.com> wrote

The code works and that is my first concern, but I am
attempting to deepen my understanding of VB.

Imagine you want to fill a parking lot with different styles of cars.
So, you grab a new car (that has interchangable parts) and assign
a new color and interior to it, and put it out in the lot. Then you
grab that same car, and assign a new color and interior to it, and
place it out in the lot. Then you grab that same car again, and
assign a third color and and interior to it and place it back out in
the lot.

How many cars are out in the lot?

There is only one, its the same car, you've just given it different
values. What you need to do is grab a new car each time, and
then assign the values. The same thing happens with objects.

If you continually add the same object to a list, then you end
up with a list where all entries point to the same object. In the
end, that object can only have one complete set of values, so
the list appears to be filled with identical objects, when in fact
its the same object, for each entry in the list. What needs to
be done is to create a new object, when a completely different
object is needed. Obviously enough, to create new objects,
the New keyword is required....

LFS

[Cor Ligthert]

Grandpa,

When you create a new object you say

Create a new object on the managed heap with all parameters set as build in
or setted in the Sub New and give it a reference in its placeholder for
where it is.

Than you *add* its reference too an arraylist collection of objects.

The arraylist itself is as well an object

You create everytime in your loop a complete new object and add it too that
collection.

At the end when the methode (even directly at every nested part) is ready,
everything created and is on the stack for that will be cleaned up so as
well all references. However your arraylist has in his collection a lot of
references too all those new objects and those will stay because the GC will
see those references.

When you set first
Private myArt as new Art than you create an objecte and you have created
globaly that reference to it in a global placeholder

When you do than
myArt as new Art than you create an object again, and set the reference in
that global placeholder for that last created object.

The reference of the first is therefore completly gone and can (and will)
be deleted by the GC.

However in this case is the last created myArt accesible from that global
placeholder and therefore from everywhere in your class. Therefore I wrote
that I would do it *probably* with dim myArt as new Art.

The reason is that I cannot see if you do something as this

myArt = Art
DoSubFillArt

Where I in that case would do
DoSubFillArt(my Art)

In the first sample directly above, (because you have set the reference of
myArt globaly), you do not need to pass it too that method the last one is
in that global reference, however in my opinion is that not nice
programming.

Is it not simple, I hope this helps?

Cor

"GrandpaB" <an*******@disc ussions.microso ft.com> schreef in bericht
news:2a******** *************** *****@phx.gbl.. .

Cor,

Thanks again for the followup. I guess that my question
boils down to: Why can I transfer existing objects, back
and forth, between AtrList(Index) and MyArt after
declaring ArtList and MyArt with:

Public ArtList as New ArrayList
Public MyArt as New Art

but when I want to add a new object to ArtList,
ArtList.Add(MyA rt), I must reinitialize MyArt with:

MyArt = New Art

or, as you suggest, with

Dim MyArt as New Art

The code works and that is my first concern, but I am
attempting to deepen my understanding of VB.

Once again thanks, GrandpaB

-----Original Message-----
Grandpa

I see it,

When you add that myArt to the arraylist than there is a

reference from the

arraylist to it.

Better, it are everytime objects in the arraylist which

are referenced and

stay referenced until they are removed from the

arraylist or the arraylist

does not exist anymore.

I did not completly look at your code. However probably

I would not do it

that way as you do it and use instead of
MyArt = New Art '??? ********* ???

Dim myArt as New art '??? ********* ???

For as far as I can see the code, do I as well not see

sense for that

Public MyArt as New Art.

You only need to create objects for in your arraylist

from the type of Art.

I hope this helps?

Cor
<an*******@di scussions.micro soft.com>

Cor,

Thanks for your assistance; yes, I think that I'm
starting to gain some insight to improve my
understanding, but I still have a puzzlement.

Let me reitterate to see if I understand. My original
statement:

Public MyArt as New Art

created MyArt as a new Art object. With this object I
was able run the subroutine:

Sub DisplayArt(ByVa l Index As Integer)
'Transfer the ArtList(Index) to MyArt and then to the form
MyArt = ArtList(Index)
MyArt2Form()
End Sub

and the statements:

Form2MyArt()
ArtList(Index)= MyArt

to sucessfully edit the various objects in ArtList, but
when I wanted to add a item to ArtList I had to include
the statement:

MyArt = New Art

So why could I use the original MyArt to edit various
items in ArtList, but when I wanted to add an item to
ArtList I needed reinitialize MyArt using the following
statements:

MyArt = New Art '??? **** ???
Form2MyArt
ArtList.Add(MyA rt)

Thanks in advance, GrandpaB

-----Original Message-----
GrandpaB

A try to answer as short as possible.

Public MyArt as New Art
Creates a new object from the class Art and does the sub New in that class

MyArt as New art
Creates a new object from the class Art and does the sub New in that class
The previous MyArt looses his reference and will
therefore be deleted by the
Garbage Collector (GC) when that start doing its job.

And not important, an object is forever created on the
managed heap.

I hope this helps?

Cor

"GrandpaB " <an*******@disc ussions.microso ft.com>

> While writing this plea for help, I think I solved my
> dilemma, but I don't know why the problem solving
> statement is necessary. The inspiration for the
> statement came from an undocumented VB example I found on
> the web. I would be most appreciative if someone could> explain why this statement is necessary and what does
it
> do:
>
> MyArt = New Art
>
> Early in the code, ArtList, MyArt & AddNew had been
> declared with the following statements:
>
> Public ArtList as New ArrayList
> Public MyArt as New Art
> Public AddNew as Boolean
>
> I am creating a Windows application which uses an
> ArrayList to contain a small amount of data. ArtList, is
> an instance of an ArrayList that will contain multiple> (up to 200) Art objects. MyArt is an instance of the
Art
> object. In the application I want to add, delete and
> edit the individual Art objects in ArtList. I am
> serializing and deserializing the ArrayList and using a> FileStream to read and write to the hard drive. This is> the code in question, and the mystery statement is
> commented with ******
>
> Private Sub btnNew_Click(By Val sender As
System.Object, _
> ByVal e As System.EventArg s) Handles btnNew.Click
>
> ClearForm() 'A sub to clear the Form's textboxes
> AddNew = True
> End Sub
>
> Private Sub btnAdd_Click(By Val sender As
System.Object, _
> ByVal e As System.EventArg s) Handles btnAdd.Click
>
> Dim Msg1 As String = "Do you want to ADD this new
> Object?"
> Dim Msg2 As String = "Update Art"
> Dim Ans As MsgBoxResult
> If FormChanged() And AddNew Then
> Ans = MsgBox(Msg1, MsgBoxStyle.Yes No, Msg2)
> If Ans = MsgBoxResult.Ye s Then
> MyArt = New Art '??? ********* ???
> Form2MyArt() 'Move textbox entries to MyArt> ArtList.Add(MyA rt)
> SaveFile() 'Serialize ArtList & write
> FileStream
> End If
> End if
> End Sub
>
.

.