How to clear controls from a form - Help Needed

[=?Utf-8?B?U2l2?=]

I have a form that I programmaticall y generate some check boxes and labels on.
Later on when I want to draw the form with different data I want to clear
the previously created items and then put some new ones on.

In my code I am doing the following:

For Each ctrl In tpMain.Controls
If TypeOf (ctrl) Is CheckBox Then
If ctrl.Name.Start sWith("chkS") Then
ctrl.Visible = False
ctrl.Dispose()
End If
End If
End if
Next

What I am finding however is that in some cases controls that I know have
been affected by the above loop are staying on the form and not being made
invisible and then being disposed.

Is there a sure fire method of removing the controls rather than the dispose
method which presumably is not always removing the control for whatever
reason??

Siv
--
Martley, Near Worcester, UK

[Rich P]

Re: How to clear controls from a form - Help Needed

It would be much easier/simpler/reliable to have an extra form with the
extra controls. When a user needs to use the other set of controls -
instead of creating a whole new set of controls just bring up the extra
form and hide the main form - or if it even matters don't do anything
with the main form. Just leave it running.

Rich

*** Sent via Developersdex http://www.developersdex.com ***

[=?Utf-8?B?U2l2?=]

Re: How to clear controls from a form - Help Needed

I can't do that because the amount of check boxes differs dramatically
between redraws, there isn't a fixed layout. On one set of data I may only
need to show 2 check boxes on another ther may be 20 or 30. I am trying to
avoid the overhead of having thousands of controls on the forma nd only
create them as I need them and then when I have finished with them destroy
them again.

The problem i think is tha the dispose method doesn't always decide to
dispose when I want it to and is probably waiting for the system to quieten
down before actioning the request.

I really need a Ctrl.delete type comand.

Siv
--
Martley, Near Worcester, UK


"Rich P" wrote:

It would be much easier/simpler/reliable to have an extra form with the
extra controls. When a user needs to use the other set of controls -
instead of creating a whole new set of controls just bring up the extra
form and hide the main form - or if it even matters don't do anything
with the main form. Just leave it running.
>
Rich
>
*** Sent via Developersdex http://www.developersdex.com ***
>

[Lloyd Sheen]

Re: How to clear controls from a form - Help Needed

Siv wrote:

I can't do that because the amount of check boxes differs dramatically
between redraws, there isn't a fixed layout. On one set of data I may only
need to show 2 check boxes on another ther may be 20 or 30. I am trying to
avoid the overhead of having thousands of controls on the forma nd only
create them as I need them and then when I have finished with them destroy
them again.
>
The problem i think is tha the dispose method doesn't always decide to
dispose when I want it to and is probably waiting for the system to quieten
down before actioning the request.
>
I really need a Ctrl.delete type comand.
>
Siv

Try this:

Create a panel onto which you will place your dynamic controls.

When you are finished with those controls, you should have a variable
for the original panel. Use the Clear method to get rid of all the
controls you created dynamically.

You now should have a blank panel upon which you can add controls with
new info.

Hope this helps
LS

[Stephany Young]

Re: How to clear controls from a form - Help Needed

For _i = tpMain.Controls .Count - 1 To 0 Step -1
Dim _ctrl = tpMain.Controls (_i)
If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS") Then
tpMain.Controls .RemoveAt(_i)
_ctrl.Dispose()
End If
Next


"Siv" <Siv@discussion s.microsoft.com wrote in message
news:ECC5102D-8DAC-4D39-B504-0F4E8BD8A6F8@mi crosoft.com...

>I have a form that I programmaticall y generate some check boxes and labels
>on.
Later on when I want to draw the form with different data I want to clear
the previously created items and then put some new ones on.
>
In my code I am doing the following:
>
For Each ctrl In tpMain.Controls
If TypeOf (ctrl) Is CheckBox Then
If ctrl.Name.Start sWith("chkS") Then
ctrl.Visible = False
ctrl.Dispose()
End If
End If
End if
Next
>
What I am finding however is that in some cases controls that I know have
been affected by the above loop are staying on the form and not being made
invisible and then being disposed.
>
Is there a sure fire method of removing the controls rather than the
dispose
method which presumably is not always removing the control for whatever
reason??
>
Siv
--
Martley, Near Worcester, UK

[=?Utf-8?B?U2l2?=]

Re: How to clear controls from a form - Help Needed

Lloyd,
Thanks for your response, these controls are already on a TabPage control
called tpMain.

When you say perform a clear, is that a method of the panel itself. Will
that clear all controls? There are a number of controls which are placed on
the TabPage at design time, would they be destroyed as well?

Interesteing idea though, I could certainly add a panel onto the TabPage in
the area where I want to display the check boxes and only add the controls
that are dynamically created to that panel.

Cheer,

Siv
--
Martley, Near Worcester, UK


"Lloyd Sheen" wrote:

Siv wrote:

I can't do that because the amount of check boxes differs dramatically
between redraws, there isn't a fixed layout. On one set of data I may only
need to show 2 check boxes on another ther may be 20 or 30. I am trying to
avoid the overhead of having thousands of controls on the forma nd only
create them as I need them and then when I have finished with them destroy
them again.

The problem i think is tha the dispose method doesn't always decide to
dispose when I want it to and is probably waiting for the system to quieten
down before actioning the request.

I really need a Ctrl.delete type comand.

Siv

>
Try this:
>
Create a panel onto which you will place your dynamic controls.
>
When you are finished with those controls, you should have a variable
for the original panel. Use the Clear method to get rid of all the
controls you created dynamically.
>
You now should have a blank panel upon which you can add controls with
new info.
>
Hope this helps
LS
>

[=?Utf-8?B?U2l2?=]

Re: How to clear controls from a form - Help Needed

Stephany,
Thanks for your reply. Can you explain why the additional command

tpMain.Controls .RemoveAt(_i)

will do the trick where just doing the dispose on its own does not?

I appreciate you gave me the answer, but I try to learn from my questions
here. Don't worry if you are too busy to reply, but if you do have time I
would appreciate it.

Siv
--
Martley, Near Worcester, UK


"Stephany Young" wrote:

For _i = tpMain.Controls .Count - 1 To 0 Step -1
Dim _ctrl = tpMain.Controls (_i)
If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS") Then
tpMain.Controls .RemoveAt(_i)
_ctrl.Dispose()
End If
Next
>
>
"Siv" <Siv@discussion s.microsoft.com wrote in message
news:ECC5102D-8DAC-4D39-B504-0F4E8BD8A6F8@mi crosoft.com...

I have a form that I programmaticall y generate some check boxes and labels
on.
Later on when I want to draw the form with different data I want to clear
the previously created items and then put some new ones on.

In my code I am doing the following:

For Each ctrl In tpMain.Controls
If TypeOf (ctrl) Is CheckBox Then
If ctrl.Name.Start sWith("chkS") Then
ctrl.Visible = False
ctrl.Dispose()
End If
End If
End if
Next

What I am finding however is that in some cases controls that I know have
been affected by the above loop are staying on the form and not being made
invisible and then being disposed.

Is there a sure fire method of removing the controls rather than the
dispose
method which presumably is not always removing the control for whatever
reason??

Siv
--
Martley, Near Worcester, UK

>
>

[Stephany Young]

Re: How to clear controls from a form - Help Needed

Your problem was that, although you were 'disposing' the control, you were
not removing it from tpMain's collection of controls. Therefore you end up
with 'phantom' controls in tpMain's control collection.

Others might argue to the contrary, but I believe that the Dispose method of
a CheckBox control does nothing special, and it certainly will not remove
itself from it's parent collection.

Therefore the code can be further simplified to:

For _i = tpMain.Controls .Count - 1 To 0 Step -1
Dim _ctrl = tpMain.Controls (_i)
If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS") Then
tpMain.Controls .RemoveAt(_i)
Next

To save you asking, the reverse loop is to ensure that iterating on the
control collection is still viable even when one or more of the iteration
actually removes an element.



"Siv" <Siv@discussion s.microsoft.com wrote in message
news:3A906198-C470-43E1-9A2D-3A3E2CDF834E@mi crosoft.com...

Stephany,
Thanks for your reply. Can you explain why the additional command
>
tpMain.Controls .RemoveAt(_i)
>
will do the trick where just doing the dispose on its own does not?
>
I appreciate you gave me the answer, but I try to learn from my questions
here. Don't worry if you are too busy to reply, but if you do have time I
would appreciate it.
>
Siv
--
Martley, Near Worcester, UK
>
>
"Stephany Young" wrote:
>

>For _i = tpMain.Controls .Count - 1 To 0 Step -1
> Dim _ctrl = tpMain.Controls (_i)
> If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS")
>Then
> tpMain.Controls .RemoveAt(_i)
> _ctrl.Dispose()
> End If
>Next
>>
>>
>"Siv" <Siv@discussion s.microsoft.com wrote in message
>news:ECC5102 D-8DAC-4D39-B504-0F4E8BD8A6F8@mi crosoft.com...

>I have a form that I programmaticall y generate some check boxes and
>labels
>on.
Later on when I want to draw the form with different data I want to
clear
the previously created items and then put some new ones on.
>
In my code I am doing the following:
>
For Each ctrl In tpMain.Controls
If TypeOf (ctrl) Is CheckBox Then
If ctrl.Name.Start sWith("chkS") Then
ctrl.Visible = False
ctrl.Dispose()
End If
End If
End if
Next
>
What I am finding however is that in some cases controls that I know
have
been affected by the above loop are staying on the form and not being
made
invisible and then being disposed.
>
Is there a sure fire method of removing the controls rather than the
dispose
method which presumably is not always removing the control for whatever
reason??
>
Siv
--
Martley, Near Worcester, UK

>>
>>

[=?Utf-8?B?U2l2?=]

Re: How to clear controls from a form - Help Needed

Stephany,

Thanks for clarifying, clearly I thought that to dispose of a control would
by inference remove it from the tpMain collection of controls. It's the old
story "never assume".

Thanks for your help.

Siv
--
Martley, Near Worcester, UK


"Stephany Young" wrote:

Your problem was that, although you were 'disposing' the control, you were
not removing it from tpMain's collection of controls. Therefore you end up
with 'phantom' controls in tpMain's control collection.
>
Others might argue to the contrary, but I believe that the Dispose method of
a CheckBox control does nothing special, and it certainly will not remove
itself from it's parent collection.
>
Therefore the code can be further simplified to:
>
For _i = tpMain.Controls .Count - 1 To 0 Step -1
Dim _ctrl = tpMain.Controls (_i)
If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS") Then
tpMain.Controls .RemoveAt(_i)
Next
>
To save you asking, the reverse loop is to ensure that iterating on the
control collection is still viable even when one or more of the iteration
actually removes an element.
>
>
>
"Siv" <Siv@discussion s.microsoft.com wrote in message
news:3A906198-C470-43E1-9A2D-3A3E2CDF834E@mi crosoft.com...

Stephany,
Thanks for your reply. Can you explain why the additional command

tpMain.Controls .RemoveAt(_i)

will do the trick where just doing the dispose on its own does not?

I appreciate you gave me the answer, but I try to learn from my questions
here. Don't worry if you are too busy to reply, but if you do have time I
would appreciate it.

Siv
--
Martley, Near Worcester, UK


"Stephany Young" wrote:

For _i = tpMain.Controls .Count - 1 To 0 Step -1
Dim _ctrl = tpMain.Controls (_i)
If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS")
Then
tpMain.Controls .RemoveAt(_i)
_ctrl.Dispose()
End If
Next
>
>
"Siv" <Siv@discussion s.microsoft.com wrote in message
news:ECC5102D-8DAC-4D39-B504-0F4E8BD8A6F8@mi crosoft.com...
I have a form that I programmaticall y generate some check boxes and
labels
on.
Later on when I want to draw the form with different data I want to
clear
the previously created items and then put some new ones on.

In my code I am doing the following:

For Each ctrl In tpMain.Controls
If TypeOf (ctrl) Is CheckBox Then
If ctrl.Name.Start sWith("chkS") Then
ctrl.Visible = False
ctrl.Dispose()
End If
End If
End if
Next

What I am finding however is that in some cases controls that I know
have
been affected by the above loop are staying on the form and not being
made
invisible and then being disposed.

Is there a sure fire method of removing the controls rather than the
dispose
method which presumably is not always removing the control for whatever
reason??

Siv
--
Martley, Near Worcester, UK
>
>

>
>

[Lloyd Sheen]

Re: How to clear controls from a form - Help Needed

Siv wrote:

Lloyd,
Thanks for your response, these controls are already on a TabPage control
called tpMain.
>
When you say perform a clear, is that a method of the panel itself. Will
that clear all controls? There are a number of controls which are placed on
the TabPage at design time, would they be destroyed as well?
>
Interesteing idea though, I could certainly add a panel onto the TabPage in
the area where I want to display the check boxes and only add the controls
that are dynamically created to that panel.
>
Cheer,
>
Siv

Clear will clear all controls on the container (panel) so you would
loose other "non-dynamic" controls. Putting a panel on the tab page
would certainly work.

LS

[=?Utf-8?B?U2l2?=]

Re: How to clear controls from a form - Help Needed

Lloyd,
I am just trying Stephany's method as it involves less changes than yours,
but if her method doesn't solve teh problem I'll redesign the form slightly
and implement your idea.

Thanks again for your help.

Siv
--
Martley, Near Worcester, UK


"Lloyd Sheen" wrote:

Siv wrote:

Lloyd,
Thanks for your response, these controls are already on a TabPage control
called tpMain.

When you say perform a clear, is that a method of the panel itself. Will
that clear all controls? There are a number of controls which are placed on
the TabPage at design time, would they be destroyed as well?

Interesteing idea though, I could certainly add a panel onto the TabPage in
the area where I want to display the check boxes and only add the controls
that are dynamically created to that panel.

Cheer,

Siv

>
Clear will clear all controls on the container (panel) so you would
loose other "non-dynamic" controls. Putting a panel on the tab page
would certainly work.
>
LS
>

[Cor Ligthert[MVP]]

Re: How to clear controls from a form - Help Needed

Siv,

Disposing is not a removing method or whateverf, it is just telling the GC
that it "can be" ready to clear up, like the GC does that automaticly when
it is really needed. Dispose is meant to put it at the garbage. As anology,
some people are the whole day busy with cleaning up there desktop (putting
it in the trash bin, which still will not be direct emptied), others do that
once a day or/and some when that is needed.

As it is about forms, you can see in your designer part of the class
(versions before 2005 normal in the class) the implementing of IDisposable
of a form.

As long as an object is referenced by something (like on a form with
controls.add) it will not be cleared as long as that has a reference,
whatever other method you call (including dispose), mostly is that by clear
them all in one time or by removing them one by one.

Cor


"Siv" <Siv@discussion s.microsoft.com schreef in bericht
news:EBBE4C00-2842-475E-97E5-01F9D7491B53@mi crosoft.com...

Stephany,
>
Thanks for clarifying, clearly I thought that to dispose of a control
would
by inference remove it from the tpMain collection of controls. It's the
old
story "never assume".
>
Thanks for your help.
>
Siv
--
Martley, Near Worcester, UK
>
>
"Stephany Young" wrote:
>

>Your problem was that, although you were 'disposing' the control, you
>were
>not removing it from tpMain's collection of controls. Therefore you end
>up
>with 'phantom' controls in tpMain's control collection.
>>
>Others might argue to the contrary, but I believe that the Dispose method
>of
>a CheckBox control does nothing special, and it certainly will not remove
>itself from it's parent collection.
>>
>Therefore the code can be further simplified to:
>>
> For _i = tpMain.Controls .Count - 1 To 0 Step -1
> Dim _ctrl = tpMain.Controls (_i)
> If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS")
>Then
>tpMain.Control s.RemoveAt(_i)
> Next
>>
>To save you asking, the reverse loop is to ensure that iterating on the
>control collection is still viable even when one or more of the iteration
>actually removes an element.
>>
>>
>>
>"Siv" <Siv@discussion s.microsoft.com wrote in message
>news:3A90619 8-C470-43E1-9A2D-3A3E2CDF834E@mi crosoft.com...

Stephany,
Thanks for your reply. Can you explain why the additional command
>
tpMain.Controls .RemoveAt(_i)
>
will do the trick where just doing the dispose on its own does not?
>
I appreciate you gave me the answer, but I try to learn from my
questions
here. Don't worry if you are too busy to reply, but if you do have time
I
would appreciate it.
>
Siv
--
Martley, Near Worcester, UK
>
>
"Stephany Young" wrote:
>
>For _i = tpMain.Controls .Count - 1 To 0 Step -1
> Dim _ctrl = tpMain.Controls (_i)
> If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS")
>Then
> tpMain.Controls .RemoveAt(_i)
> _ctrl.Dispose()
> End If
>Next
>>
>>
>"Siv" <Siv@discussion s.microsoft.com wrote in message
>news:ECC5102 D-8DAC-4D39-B504-0F4E8BD8A6F8@mi crosoft.com...
>I have a form that I programmaticall y generate some check boxes and
>labels
>on.
Later on when I want to draw the form with different data I want to
clear
the previously created items and then put some new ones on.
>
In my code I am doing the following:
>
For Each ctrl In tpMain.Controls
If TypeOf (ctrl) Is CheckBox Then
If ctrl.Name.Start sWith("chkS") Then
ctrl.Visible = False
ctrl.Dispose()
End If
End If
End if
Next
>
What I am finding however is that in some cases controls that I know
have
been affected by the above loop are staying on the form and not
being
made
invisible and then being disposed.
>
Is there a sure fire method of removing the controls rather than the
dispose
method which presumably is not always removing the control for
whatever
reason??
>
Siv
--
Martley, Near Worcester, UK
>>
>>

>>
>>

[Jack Jackson]

Re: How to clear controls from a form - Help Needed

Cor,

I'm sure it is useless to argue with you, but it is misleading to say
that the purpose of Dispose is to tell the GC that the object " 'can
be' ready to clear up".

The purpose if Dispose is to release unmanaged resources. For
Controls, that would mostly be the Windows handle for the associated
Windows control. If you fail to call Dispose for a Control that has
allocated a Windows handle, then the handle might no be freed for a
very long time, and if you do this enough times you might run out of
Windows handles.

On Tue, 5 Aug 2008 06:47:35 +0200, "Cor Ligthert[MVP]"
<notmyfirstname @planet.nlwrote :

>Siv,
>
>Disposing is not a removing method or whateverf, it is just telling the GC
>that it "can be" ready to clear up, like the GC does that automaticly when
>it is really needed. Dispose is meant to put it at the garbage. As anology,
>some people are the whole day busy with cleaning up there desktop (putting
>it in the trash bin, which still will not be direct emptied), others do that
>once a day or/and some when that is needed.
>
>As it is about forms, you can see in your designer part of the class
>(versions before 2005 normal in the class) the implementing of IDisposable
>of a form.
>
>As long as an object is referenced by something (like on a form with
>controls.add ) it will not be cleared as long as that has a reference,
>whatever other method you call (including dispose), mostly is that by clear
>them all in one time or by removing them one by one.
>
>Cor
>
>
>"Siv" <Siv@discussion s.microsoft.com schreef in bericht
>news:EBBE4C0 0-2842-475E-97E5-01F9D7491B53@mi crosoft.com...

>Stephany,
>>
>Thanks for clarifying, clearly I thought that to dispose of a control
>would
>by inference remove it from the tpMain collection of controls. It's the
>old
>story "never assume".
>>
>Thanks for your help.
>>
>Siv
>--
>Martley, Near Worcester, UK
>>
>>
>"Stephany Young" wrote:
>>

>>Your problem was that, although you were 'disposing' the control, you
>>were
>>not removing it from tpMain's collection of controls. Therefore you end
>>up
>>with 'phantom' controls in tpMain's control collection.
>>>
>>Others might argue to the contrary, but I believe that the Dispose method
>>of
>>a CheckBox control does nothing special, and it certainly will not remove
>>itself from it's parent collection.
>>>
>>Therefore the code can be further simplified to:
>>>
>> For _i = tpMain.Controls .Count - 1 To 0 Step -1
>> Dim _ctrl = tpMain.Controls (_i)
>> If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS")
>>Then
>>tpMain.Contro ls.RemoveAt(_i)
>> Next
>>>
>>To save you asking, the reverse loop is to ensure that iterating on the
>>control collection is still viable even when one or more of the iteration
>>actually removes an element.
>>>
>>>
>>>
>>"Siv" <Siv@discussion s.microsoft.com wrote in message
>>news:3A9061 98-C470-43E1-9A2D-3A3E2CDF834E@mi crosoft.com...
>Stephany,
>Thanks for your reply. Can you explain why the additional command
>>
>tpMain.Control s.RemoveAt(_i)
>>
>will do the trick where just doing the dispose on its own does not?
>>
>I appreciate you gave me the answer, but I try to learn from my
>questions
>here. Don't worry if you are too busy to reply, but if you do have time
>I
>would appreciate it.
>>
>Siv
>--
>Martley, Near Worcester, UK
>>
>>
>"Stephany Young" wrote:
>>
>>For _i = tpMain.Controls .Count - 1 To 0 Step -1
>> Dim _ctrl = tpMain.Controls (_i)
>> If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS")
>>Then
>> tpMain.Controls .RemoveAt(_i)
>> _ctrl.Dispose()
>> End If
>>Next
>>>
>>>
>>"Siv" <Siv@discussion s.microsoft.com wrote in message
>>news:ECC510 2D-8DAC-4D39-B504-0F4E8BD8A6F8@mi crosoft.com...
>>I have a form that I programmaticall y generate some check boxes and
>>labels
>>on.
>Later on when I want to draw the form with different data I want to
>clear
>the previously created items and then put some new ones on.
>>
>In my code I am doing the following:
>>
>For Each ctrl In tpMain.Controls
>If TypeOf (ctrl) Is CheckBox Then
> If ctrl.Name.Start sWith("chkS") Then
> ctrl.Visible = False
> ctrl.Dispose()
> End If
> End If
>End if
>Next
>>
>What I am finding however is that in some cases controls that I know
>have
>been affected by the above loop are staying on the form and not
>being
>made
>invisible and then being disposed.
>>
>Is there a sure fire method of removing the controls rather than the
>dispose
>method which presumably is not always removing the control for
>whatever
>reason??
>>
>Siv
>--
>Martley, Near Worcester, UK
>>>
>>>
>>>
>>>

[Cor Ligthert [MVP]]

Re: How to clear controls from a form - Help Needed

Jack,

Absolute true, I had it first in my message but was afraid that it would
create to much confusion (and discussion). I normally try to write that part
exactly like you do, and it is very important in the case there are
unmanaged resources used. Which is AFAIK by instance not the fact "in"
controls. (but can be used in objects that controls are using).

I have seen it so much written in the context like I did now, so I did that
a bit like that to avoid a discussion. Normally I don't use that because it
is for me really a minor aspect to take action to clear 100bytes memory a
little bit quicker while I have 1Gb not used.

Cor

"Jack Jackson" <jjackson@cinno vations.netschr eef in bericht
news:6trf94l793 52peqi1qep0et83 j3ut6qdev@4ax.c om...

Cor,
>
I'm sure it is useless to argue with you, but it is misleading to say
that the purpose of Dispose is to tell the GC that the object " 'can
be' ready to clear up".
>
The purpose if Dispose is to release unmanaged resources. For
Controls, that would mostly be the Windows handle for the associated
Windows control. If you fail to call Dispose for a Control that has
allocated a Windows handle, then the handle might no be freed for a
very long time, and if you do this enough times you might run out of
Windows handles.
>
On Tue, 5 Aug 2008 06:47:35 +0200, "Cor Ligthert[MVP]"
<notmyfirstname @planet.nlwrote :
>

>>Siv,
>>
>>Disposing is not a removing method or whateverf, it is just telling the GC
>>that it "can be" ready to clear up, like the GC does that automaticly when
>>it is really needed. Dispose is meant to put it at the garbage. As
>>anology,
>>some people are the whole day busy with cleaning up there desktop (putting
>>it in the trash bin, which still will not be direct emptied), others do
>>that
>>once a day or/and some when that is needed.
>>
>>As it is about forms, you can see in your designer part of the class
>>(versions before 2005 normal in the class) the implementing of IDisposable
>>of a form.
>>
>>As long as an object is referenced by something (like on a form with
>>controls.ad d) it will not be cleared as long as that has a reference,
>>whatever other method you call (including dispose), mostly is that by
>>clear
>>them all in one time or by removing them one by one.
>>
>>Cor
>>
>>
>>"Siv" <Siv@discussion s.microsoft.com schreef in bericht
>>news:EBBE4C 00-2842-475E-97E5-01F9D7491B53@mi crosoft.com...

>>Stephany,
>>>
>>Thanks for clarifying, clearly I thought that to dispose of a control
>>would
>>by inference remove it from the tpMain collection of controls. It's the
>>old
>>story "never assume".
>>>
>>Thanks for your help.
>>>
>>Siv
>>--
>>Martley, Near Worcester, UK
>>>
>>>
>>"Stephany Young" wrote:
>>>
>>>Your problem was that, although you were 'disposing' the control, you
>>>were
>>>not removing it from tpMain's collection of controls. Therefore you
>>>end
>>>up
>>>with 'phantom' controls in tpMain's control collection.
>>>>
>>>Others might argue to the contrary, but I believe that the Dispose
>>>method
>>>of
>>>a CheckBox control does nothing special, and it certainly will not
>>>remove
>>>itself from it's parent collection.
>>>>
>>>Therefore the code can be further simplified to:
>>>>
>>> For _i = tpMain.Controls .Count - 1 To 0 Step -1
>>> Dim _ctrl = tpMain.Controls (_i)
>>> If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS")
>>>Then
>>>tpMain.Contr ols.RemoveAt(_i )
>>> Next
>>>>
>>>To save you asking, the reverse loop is to ensure that iterating on the
>>>control collection is still viable even when one or more of the
>>>iteration
>>>actually removes an element.
>>>>
>>>>
>>>>
>>>"Siv" <Siv@discussion s.microsoft.com wrote in message
>>>news:3A90619 8-C470-43E1-9A2D-3A3E2CDF834E@mi crosoft.com...
>>Stephany,
>>Thanks for your reply. Can you explain why the additional command
>>>
>>tpMain.Contro ls.RemoveAt(_i)
>>>
>>will do the trick where just doing the dispose on its own does not?
>>>
>>I appreciate you gave me the answer, but I try to learn from my
>>questions
>>here. Don't worry if you are too busy to reply, but if you do have
>>time
>>I
>>would appreciate it.
>>>
>>Siv
>>--
>>Martley, Near Worcester, UK
>>>
>>>
>>"Stephany Young" wrote:
>>>
>>>For _i = tpMain.Controls .Count - 1 To 0 Step -1
>>> Dim _ctrl = tpMain.Controls (_i)
>>> If TypeOf (_ctrl) Is CheckBox AndAlso
>>>_ctrl.Name.S tartsWith("chkS ")
>>>Then
>>> tpMain.Controls .RemoveAt(_i)
>>> _ctrl.Dispose()
>>> End If
>>>Next
>>>>
>>>>
>>>"Siv" <Siv@discussion s.microsoft.com wrote in message
>>>news:ECC5102 D-8DAC-4D39-B504-0F4E8BD8A6F8@mi crosoft.com...
>>>I have a form that I programmaticall y generate some check boxes and
>>>labels
>>>on.
>>Later on when I want to draw the form with different data I want
>>to
>>clear
>>the previously created items and then put some new ones on.
>>>
>>In my code I am doing the following:
>>>
>>For Each ctrl In tpMain.Controls
>>If TypeOf (ctrl) Is CheckBox Then
>> If ctrl.Name.Start sWith("chkS") Then
>> ctrl.Visible = False
>> ctrl.Dispose()
>> End If
>> End If
>>End if
>>Next
>>>
>>What I am finding however is that in some cases controls that I
>>know
>>have
>>been affected by the above loop are staying on the form and not
>>being
>>made
>>invisible and then being disposed.
>>>
>>Is there a sure fire method of removing the controls rather than
>>the
>>dispose
>>method which presumably is not always removing the control for
>>whatever
>>reason??
>>>
>>Siv
>>--
>>Martley, Near Worcester, UK
>>>>
>>>>
>>>>
>>>>

[Cor Ligthert [MVP]]

Re: How to clear controls from a form - Help Needed

Jack,

Maybe should I have added this piece of code that is created by most
designers.
Which AFAIK is done by instance at every close of a form.

\\\
'Form overrides dispose to clean up the component list.
<System.Diagnos tics.DebuggerNo nUserCode()_
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
Try
If disposing AndAlso components IsNot Nothing Then
components.Disp ose()
End If
Finally
MyBase.Dispose( disposing)
End Try
End Sub
///

Cor

"Jack Jackson" <jjackson@cinno vations.netschr eef in bericht
news:6trf94l793 52peqi1qep0et83 j3ut6qdev@4ax.c om...

Cor,
>
I'm sure it is useless to argue with you, but it is misleading to say
that the purpose of Dispose is to tell the GC that the object " 'can
be' ready to clear up".
>
The purpose if Dispose is to release unmanaged resources. For
Controls, that would mostly be the Windows handle for the associated
Windows control. If you fail to call Dispose for a Control that has
allocated a Windows handle, then the handle might no be freed for a
very long time, and if you do this enough times you might run out of
Windows handles.
>
On Tue, 5 Aug 2008 06:47:35 +0200, "Cor Ligthert[MVP]"
<notmyfirstname @planet.nlwrote :
>

>>Siv,
>>
>>Disposing is not a removing method or whateverf, it is just telling the GC
>>that it "can be" ready to clear up, like the GC does that automaticly when
>>it is really needed. Dispose is meant to put it at the garbage. As
>>anology,
>>some people are the whole day busy with cleaning up there desktop (putting
>>it in the trash bin, which still will not be direct emptied), others do
>>that
>>once a day or/and some when that is needed.
>>
>>As it is about forms, you can see in your designer part of the class
>>(versions before 2005 normal in the class) the implementing of IDisposable
>>of a form.
>>
>>As long as an object is referenced by something (like on a form with
>>controls.ad d) it will not be cleared as long as that has a reference,
>>whatever other method you call (including dispose), mostly is that by
>>clear
>>them all in one time or by removing them one by one.
>>
>>Cor
>>
>>
>>"Siv" <Siv@discussion s.microsoft.com schreef in bericht
>>news:EBBE4C 00-2842-475E-97E5-01F9D7491B53@mi crosoft.com...

>>Stephany,
>>>
>>Thanks for clarifying, clearly I thought that to dispose of a control
>>would
>>by inference remove it from the tpMain collection of controls. It's the
>>old
>>story "never assume".
>>>
>>Thanks for your help.
>>>
>>Siv
>>--
>>Martley, Near Worcester, UK
>>>
>>>
>>"Stephany Young" wrote:
>>>
>>>Your problem was that, although you were 'disposing' the control, you
>>>were
>>>not removing it from tpMain's collection of controls. Therefore you
>>>end
>>>up
>>>with 'phantom' controls in tpMain's control collection.
>>>>
>>>Others might argue to the contrary, but I believe that the Dispose
>>>method
>>>of
>>>a CheckBox control does nothing special, and it certainly will not
>>>remove
>>>itself from it's parent collection.
>>>>
>>>Therefore the code can be further simplified to:
>>>>
>>> For _i = tpMain.Controls .Count - 1 To 0 Step -1
>>> Dim _ctrl = tpMain.Controls (_i)
>>> If TypeOf (_ctrl) Is CheckBox AndAlso _ctrl.Name.Star tsWith("chkS")
>>>Then
>>>tpMain.Contr ols.RemoveAt(_i )
>>> Next
>>>>
>>>To save you asking, the reverse loop is to ensure that iterating on the
>>>control collection is still viable even when one or more of the
>>>iteration
>>>actually removes an element.
>>>>
>>>>
>>>>
>>>"Siv" <Siv@discussion s.microsoft.com wrote in message
>>>news:3A90619 8-C470-43E1-9A2D-3A3E2CDF834E@mi crosoft.com...
>>Stephany,
>>Thanks for your reply. Can you explain why the additional command
>>>
>>tpMain.Contro ls.RemoveAt(_i)
>>>
>>will do the trick where just doing the dispose on its own does not?
>>>
>>I appreciate you gave me the answer, but I try to learn from my
>>questions
>>here. Don't worry if you are too busy to reply, but if you do have
>>time
>>I
>>would appreciate it.
>>>
>>Siv
>>--
>>Martley, Near Worcester, UK
>>>
>>>
>>"Stephany Young" wrote:
>>>
>>>For _i = tpMain.Controls .Count - 1 To 0 Step -1
>>> Dim _ctrl = tpMain.Controls (_i)
>>> If TypeOf (_ctrl) Is CheckBox AndAlso
>>>_ctrl.Name.S tartsWith("chkS ")
>>>Then
>>> tpMain.Controls .RemoveAt(_i)
>>> _ctrl.Dispose()
>>> End If
>>>Next
>>>>
>>>>
>>>"Siv" <Siv@discussion s.microsoft.com wrote in message
>>>news:ECC5102 D-8DAC-4D39-B504-0F4E8BD8A6F8@mi crosoft.com...
>>>I have a form that I programmaticall y generate some check boxes and
>>>labels
>>>on.
>>Later on when I want to draw the form with different data I want
>>to
>>clear
>>the previously created items and then put some new ones on.
>>>
>>In my code I am doing the following:
>>>
>>For Each ctrl In tpMain.Controls
>>If TypeOf (ctrl) Is CheckBox Then
>> If ctrl.Name.Start sWith("chkS") Then
>> ctrl.Visible = False
>> ctrl.Dispose()
>> End If
>> End If
>>End if
>>Next
>>>
>>What I am finding however is that in some cases controls that I
>>know
>>have
>>been affected by the above loop are staying on the form and not
>>being
>>made
>>invisible and then being disposed.
>>>
>>Is there a sure fire method of removing the controls rather than
>>the
>>dispose
>>method which presumably is not always removing the control for
>>whatever
>>reason??
>>>
>>Siv
>>--
>>Martley, Near Worcester, UK
>>>>
>>>>
>>>>
>>>>