weird error upon form loading

[iwdu15]

hi, i have a few forms in my project. when i load form1 (startup for) all is
fine, then i open another one and use a login screen to call yet another and
all is still fine, but then when i try to open another form from a 3rd form,
it gives this error on form1

"An unhandled exception of type 'System.NullRef erenceException ' occurred in
Unknown Module.

Additional information: Object reference not set to an instance of an object."

yet the form has opened, but then the program just crashes...

heres how i open the form:

Dim frm As New OldBrackets
Close()
frm.Show()

im puzzled so any help is awsome

[Chris]

Re: weird error upon form loading

iwdu15 wrote:[color=blue]
> hi, i have a few forms in my project. when i load form1 (startup for) all is
> fine, then i open another one and use a login screen to call yet another and
> all is still fine, but then when i try to open another form from a 3rd form,
> it gives this error on form1
>
> "An unhandled exception of type 'System.NullRef erenceException ' occurred in
> Unknown Module.
>
> Additional information: Object reference not set to an instance of an object."
>
> yet the form has opened, but then the program just crashes...
>
> heres how i open the form:
>
> Dim frm As New OldBrackets
> Close()
> frm.Show()
>
> im puzzled so any help is awsome[/color]


I think this is what is happening....

Dim frm As New OldBrackets <- Create a new form store it in frm
Close() <- Close current form and all it's variables including frm
frm.Show() <- frm has been released, now you get your error.

Maybe try:
Dim frm As New OldBrackets
frm.Show()
Close()

[Armin Zingler]

Re: weird error upon form loading

"iwdu15" <iwdu15@discuss ions.microsoft. com> schrieb[color=blue]
> hi, i have a few forms in my project. when i load form1 (startup
> for) all is fine, then i open another one and use a login screen to
> call yet another and all is still fine, but then when i try to open
> another form from a 3rd form, it gives this error on form1
>
> "An unhandled exception of type 'System.NullRef erenceException '
> occurred in Unknown Module.
>
> Additional information: Object reference not set to an instance of
> an object."
>
> yet the form has opened, but then the program just crashes...
>
> heres how i open the form:
>
> Dim frm As New OldBrackets
> Close()
> frm.Show()
>
> im puzzled so any help is awsome[/color]


What is the line throwing the error? Please post the callstack when the
error occurs (menu debug -> windows -> callstack).


Armin

[Armin Zingler]

Re: weird error upon form loading

"Chris" <no@spam.com> schrieb[color=blue]
> iwdu15 wrote:[color=green]
> > hi, i have a few forms in my project. when i load form1 (startup
> > for) all is fine, then i open another one and use a login screen
> > to call yet another and all is still fine, but then when i try to
> > open another form from a 3rd form, it gives this error on form1
> >
> > "An unhandled exception of type 'System.NullRef erenceException '
> > occurred in Unknown Module.
> >
> > Additional information: Object reference not set to an instance of
> > an object."
> >
> > yet the form has opened, but then the program just crashes...
> >
> > heres how i open the form:
> >
> > Dim frm As New OldBrackets
> > Close()
> > frm.Show()
> >
> > im puzzled so any help is awsome[/color]
>
>
> I think this is what is happening....
>
> Dim frm As New OldBrackets <- Create a new form store it in frm
> Close() <- Close current form and all it's variables including frm
> frm.Show() <- frm has been released, now you get your error.[/color]


This is not right. Close closes the form, i.e. the corresponding window,
nothing else. frm is a local variable and still holds a reference to the new
Form, thus frm is not Nothing after closing the form and frm.show can not
throw the exception - maybe within one of the sub procedures but not because
frm is nothing.


Armin

[color=blue]
> Maybe try:
> Dim frm As New OldBrackets
> frm.Show()
> Close()
>[/color]

[iwdu15]

Re: weird error upon form loading

this is gunna throw all you guys for a loop....it shows an error, highlighted
in green on this line:

Public Class Form1

this has got me stumped, i have a few imports so maybe its with one of them,
although i dont get any errors on them, but here they are anyway

Imports System.Runtime. InteropServices
Imports System.Drawing
Imports System.Drawing. Drawing2D
Imports MsdnMag

so anyone that can help id be grateful

[iwdu15]

Re: weird error upon form loading

i thought it might be an error with the gererated code so i made a new form
and copyied all the code (besides the windows designer code) to the new form
and remade the second form to be exactly like the first but it gsave the
error on the new form also

[Armin Zingler]

Re: weird error upon form loading

"iwdu15" <iwdu15@discuss ions.microsoft. com> schrieb[color=blue]
> i thought it might be an error with the gererated code so i made a
> new form and copyied all the code (besides the windows designer
> code) to the new form and remade the second form to be exactly like
> the first but it gsave the error on the new form also[/color]


Without posting the callstack as suggested, I am not able to help you.


Armin

[iwdu15]

Re: weird error upon form loading

sorry, my bad, heres what i copied from the call stack
[color=blue]
> Brackets.exe!Br ackets.Main.Mai n() Line 6 + 0x1d bytes Basic[/color]

[Armin Zingler]

Re: weird error upon form loading

"iwdu15" <iwdu15@discuss ions.microsoft. com> schrieb[color=blue]
> sorry, my bad, heres what i copied from the call stack
>[color=green]
> > Brackets.exe!Br ackets.Main.Mai n() Line 6 + 0x1d bytes Basic[/color]
>[/color]

This is the complete callstack? Well, possible. I wonder why the error
occurs there because you write it doesn't happen before you open another
form.

What if you add this sub to your startup form:

shared sub main
dim f as new form1 'assuming form1 is the startup form
application.run (f)
end sub

Where does the error occur now, and what does the callstack say?

More questions: Are you working with threads? Do you have shared members in
your startup Form?


Armin

[iwdu15]

Re: weird error upon form loading

when i did the shared sub main thing, it still happened and the call stack
was empty, as for threads....id ont think im using them...im guessing if i
dont kno them im prob not, so the same for shared members...and for my
startup form, all it does is load settings from an ini file, which has worked
since i started this project, save settings, and open new forms based on
button clicks. but when i open a certain form, which doesnt have a formload
event, it crashes, if u need more source code just tell me

[iwdu15]

Re: weird error upon form loading

ok well another weird thing, when i made the form (the one that when it
loads, gives an error on another form) the startup form, all was well and good

[Armin Zingler]

Re: weird error upon form loading

"iwdu15" <iwdu15@discuss ions.microsoft. com> schrieb[color=blue]
> when i did the shared sub main thing, it still happened and the call
> stack was empty, as for threads....[/color]


Did you pause (ctrl+break) the program? There must be something in the
callstack.
[color=blue]
> id ont think im using them...im
> guessing if i dont kno them im prob not, so the same for shared
> members...and for my startup form, all it does is load settings from
> an ini file, which has worked since i started this project, save
> settings, and open new forms based on button clicks. but when i open
> a certain form, which doesnt have a formload event, it crashes, if u
> need more source code just tell me[/color]


If it's possible to send me the whole project (zipped, please), send it to
az.nospam@freen et.de but insert an underscore between "no" and "spam" in the
address before.


Armin

[iwdu15]

Re: weird error upon form loading

sent, and thanks a ton

[Armin Zingler]

Re: weird error upon form loading

"iwdu15" <iwdu15@discuss ions.microsoft. com> schrieb[color=blue]
> sent, and thanks a ton[/color]

Hew.. pretty big project... I'll have a look. :-)


Armin

[Armin Zingler]

Re: weird error upon form loading

"iwdu15" <iwdu15@discuss ions.microsoft. com> schrieb[color=blue]
> hi, i have a few forms in my project. when i load form1 (startup
> for) all is fine, then i open another one and use a login screen to
> call yet another and all is still fine, but then when i try to open
> another form from a 3rd form, it gives this error on form1
>
> "An unhandled exception of type 'System.NullRef erenceException '
> occurred in Unknown Module.
>
> Additional information: Object reference not set to an instance of
> an object."
>
> yet the form has opened, but then the program just crashes...
>
> heres how i open the form:
>
> Dim frm As New OldBrackets
> Close()
> frm.Show()
>
> im puzzled so any help is awsome[/color]


After he sent the project to me, it turned out to be the following problem:

http://groups.google.com/groups?as_q=combobox+close+selectedindexchanged+nullreferenceexception&as_ugroup=microsoft.public.dotnet.*

Easiest way to reproduce the problem is to add a combobox (add some items)
in a new empty project and call Me.Close in it's selectedindexch anged event.

I didn't have a solution. Anybody?


Armin