For Each loop problem - (Bug?)

**Herfried K. Wagner [MVP]** · Nov 21 '05, 10:11 PM

Re: For Each loop problem - (Bug?)

"B. Chernick" <BChernick@disc ussions.microso ft.com> schrieb:[color=blue]
> Is this a bug or just bad programming? I've never encountered this
> problem
> before.
> (Bare minimum sample form to illustrate.) I've also tried this with a
> class. Same result.
> The error is: For loop control variable 'd' already in use by an
> enclosing
> For loop.
> -----------------------------------------
> Structure docdefs
> Public c As Collection
> Public d As Integer
> End Structure
>
> Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
> System.EventArg s) Handles MyBase.Load
> Dim a As docdefs
> Dim b As docdefs
>
> For Each a.d In a.c
> For Each b.d In b.c
> ' some code here
> Next
> Next[/color]

I consider this a bug because it's clear that the same variable is not being
reused. I'll investigate...

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

**Phil G.** · Nov 21 '05, 10:11 PM

Re: For Each loop problem - (Bug?)

I'm sure someone else will post why but one solution would be :

Structure docdefs
Public c As Collection
Public d As Integer
End Structure

Structure docdefs1
Public c As Collection
Public d As Integer
End Structure

Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
System.EventArg s) Handles MyBase.Load
Dim a As New docdefs
Dim b As New docdefs1

For Each a.d In a.c
For Each b.d In b.c
' some code here
Next
Next

End Sub

Rgds, Phil

"B. Chernick" <BChernick@disc ussions.microso ft.com> wrote in message
news:115D8BC6-03E5-4F75-BADA-07C5D1EE5571@mi crosoft.com...[color=blue]
> Is this a bug or just bad programming? I've never encountered this
> problem
> before.
> (Bare minimum sample form to illustrate.) I've also tried this with a
> class. Same result.
> The error is: For loop control variable 'd' already in use by an
> enclosing
> For loop.
> -----------------------------------------
> Structure docdefs
> Public c As Collection
> Public d As Integer
> End Structure
>
> Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
> System.EventArg s) Handles MyBase.Load
> Dim a As docdefs
> Dim b As docdefs
>
> For Each a.d In a.c
> For Each b.d In b.c
> ' some code here
> Next
> Next
>
> End Sub
>[/color]

**B. Chernick** · Nov 21 '05, 10:12 PM

Re: For Each loop problem - (Bug?)

I suppose so but the whole purpose of my code was to combine all related
items in one structure definition. This sort of defeats the whole purpose.

"Phil G." wrote:
[color=blue]
> I'm sure someone else will post why but one solution would be :
>
> Structure docdefs
> Public c As Collection
> Public d As Integer
> End Structure
>
> Structure docdefs1
> Public c As Collection
> Public d As Integer
> End Structure
>
> Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
> System.EventArg s) Handles MyBase.Load
> Dim a As New docdefs
> Dim b As New docdefs1
>
> For Each a.d In a.c
> For Each b.d In b.c
> ' some code here
> Next
> Next
>
> End Sub
>
> Rgds, Phil
>
> "B. Chernick" <BChernick@disc ussions.microso ft.com> wrote in message
> news:115D8BC6-03E5-4F75-BADA-07C5D1EE5571@mi crosoft.com...[color=green]
> > Is this a bug or just bad programming? I've never encountered this
> > problem
> > before.
> > (Bare minimum sample form to illustrate.) I've also tried this with a
> > class. Same result.
> > The error is: For loop control variable 'd' already in use by an
> > enclosing
> > For loop.
> > -----------------------------------------
> > Structure docdefs
> > Public c As Collection
> > Public d As Integer
> > End Structure
> >
> > Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
> > System.EventArg s) Handles MyBase.Load
> > Dim a As docdefs
> > Dim b As docdefs
> >
> > For Each a.d In a.c
> > For Each b.d In b.c
> > ' some code here
> > Next
> > Next
> >
> > End Sub
> >[/color]
>
>
>[/color]

**_AnonCoward** · Nov 21 '05, 10:12 PM

Re: For Each loop problem - (Bug?)

"B. Chernick" <BChernick@disc ussions.microso ft.com> wrote in message
news:115D8BC6-03E5-4F75-BADA-07C5D1EE5571@mi crosoft.com...
:
: Is this a bug or just bad programming? I've never encountered this
: problem before.
: (Bare minimum sample form to illustrate.) I've also tried this with a
: class. Same result.
: The error is: For loop control variable 'd' already in use by an
: enclosing For loop.
: -----------------------------------------
: Structure docdefs
: Public c As Collection
: Public d As Integer
: End Structure
:
: Private Sub Form1_Load(ByVa l sender As System.Object, ByVal e As
: System.EventArg s) Handles MyBase.Load
: Dim a As docdefs
: Dim b As docdefs
:
: For Each a.d In a.c
: For Each b.d In b.c
: ' some code here
: Next
: Next
:
: End Sub

While this may be a bug, I think the actual root problem is that your
are using a member variable of the docdefs structure as your enumerator
(don't know why that would be a problem mind you, but there it is). I
don't know if this will do what you're looking for but how about the
following?

---------------------------------------------------------
Private Sub Form1_Load(ByVa l sender As System.Object, _
ByVal e As System.EventArg s) Handles MyBase.Load
Dim a As New docdefs
Dim b As New docdefs

'since members in a structure can't be declared 'New', you'll
'have to manually instantiate them here
a.c = New Collection
b.c = New Collection

'Use a dedicated enumerator for each loop rather than the
'member variable a.d / b.d
For Each d1 As Integer In a.c
For Each d2 As Integer In b.c
' some code here
Next
Next

End Sub

Structure docdefs
Public c As Collection

'this isn't necessary unless there is another purpose not
'disclosed in the original posting.
'Public d As Integer
End Structure
---------------------------------------------------------

Note, this won't work unless the member collection 'c' in docdefs only
contains integer values (or strings that can beconverted to iteger).
For example, the following will compile and run:

---------------------------------------------------------
Dim a As New docdefs
Dim b As New docdefs
a.c = New Collection
b.c = New Collection

a.c.add(1)
a.c.add("2")
b.c.add(3)
b.c.add("4")

For Each d1 As Integer In a.c
Console.WriteLi ne("d1: " & d1)

For Each d2 As Integer In b.c
Console.WriteLi ne(vbTab & "d2: " & d2)

Next
Next
---------------------------------------------------------

This will produce the output:

---------------------------------------------------------
d1: 1
d2: 3
d2: 4
d1: 2
d2: 3
d2: 4
---------------------------------------------------------

However, the following will thrown an exception:

---------------------------------------------------------
Dim a As New docdefs
Dim b As New docdefs
a.c = New Collection
b.c = New Collection

a.c.add(1)
a.c.add("2")
b.c.add(3)
b.c.add("A") '<- offending line

Try
For Each d1 As Integer In a.c
Console.WriteLi ne("d1: " & d1)

For Each d2 As Integer In b.c
Console.WriteLi ne(vbTab & "d2: " & d2)

Next
Next
Catch e As Exception
Console.WriteLi ne(e.message)
End Try
---------------------------------------------------------

This generates the following output:

---------------------------------------------------------
d1: 1
d2: 3
Cast from string "A" to type 'Integer' is not valid.
---------------------------------------------------------

HTH

Ralf
--
----------------------------------------------------------
* ^~^ ^~^ *
* _ {~ ~} {~ ~} _ *
* /_``>*< >*<''_\ *
* (\--_)++) (++(_--/) *
----------------------------------------------------------
There are no advanced students in Aikido - there are only
competent beginners. There are no advanced techniques -
only the correct application of basic principles.

**Herfried K. Wagner [MVP]** · Nov 21 '05, 10:15 PM

Re: For Each loop problem - (Bug?)

Addendum:

Bug report:

<URL:http://lab.msdn.micros oft.com/productfeedback/viewfeedback.as px?feedbackid=a b8da617-37fd-4431-a0e3-75c70e94f1c1>

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

For Each loop problem - (Bug?)

For Each loop problem - (Bug?)

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