Null Reference error in VB3NET2003

[Paul S. Natanson]

What is a Null Reference error and how do I fix it?

My newly installed VB.Net2003 gives me a "Microsoft
Development Environment" error message box EVERY time I
try to run/start ANY project - even very simple ones.

The error says:

"An unhandled exception of
type 'System.NullRef erenceException ' occurred in
system.windows. forms.dll. Additional information: Object
reference not set to an instance of an object."

As best I can determine from the debugger and the help
screens, the error has something to do with de-referencing
the form. But I don't even know what that means.

This happens even when I open a project that contains
nothing more than an empty form. And reinstalling
VB.NET2003Stand ard did not solve the problem.

What does this error mean? What might be causing it? And
how do I fix it?

Because I doubt that I will ever be able to find this
bulletin board / news group again, I would be most
grateful if, after posting your reply here, you would also
please send it to me in an email. My email address is
pa********@conc entricxxx.netxxx with the xxx's removed.

Thanks, Paul S. Natanson (Phone [phone] AM - 9
PM eastern USA time) pa********@conc entricxxx.netxxx
(remove xxxx's from email address). December 22, 2003

[Cor]

Hi Paul,

What is a Null Reference error and how do I fix it?

I try to tell it on a simple way.

When you declare a simple class global in your program you do
Private myClassInProgra m as myclass
But then the object (reference) does not exist.

Then you can create it everywhere with
myClassInProgra m = new myclass
And the object and the reference exist in your complete program

You can also do in a Sub or a Function
dim myClassInProgra m as new myclass
Then it only exist in the sub or function where it is declared and created.

I keep it with this, others I think I only confuse you, this is the basic.

I hope this helps?

Cor

[Herfried K. Wagner [MVP]]

* "Paul S. Natanson" <an*******@disc ussions.microso ft.com> scripsit:

My newly installed VB.Net2003 gives me a "Microsoft
Development Environment" error message box EVERY time I
try to run/start ANY project - even very simple ones.

The error says:

"An unhandled exception of
type 'System.NullRef erenceException ' occurred in
system.windows. forms.dll. Additional information: Object
reference not set to an instance of an object."

As best I can determine from the debugger and the help
screens, the error has something to do with de-referencing
the form. But I don't even know what that means.

This happens even when I open a project that contains
nothing more than an empty form. And reinstalling
VB.NET2003Stand ard did not solve the problem.

Seems to be an error in the project, not in the IDE. Does this even
occur when you create a completely new project with a single form (not
opening an existing project)? Go into the "bin" folder of your
application and start the executable file: Does this throw the
exception too? Did you have any beta or trial versions of VS.NET
installed on the machine?

--
Herfried K. Wagner [MVP]
<http://www.mvps.org/dotnet>

-----Original Message-----
* "Paul S. Natanson" <an*******@disc ussions.microso ft.com> scripsit:

My newly installed VB.Net2003 gives me a "Microsoft
Development Environment" error message box EVERY time I try to run/start ANY project - even very simple ones.

The error says:

"An unhandled exception of
type 'System.NullRef erenceException ' occurred in
system.windows. forms.dll. Additional information: Object reference not set to an instance of an object."

As best I can determine from the debugger and the help
screens, the error has something to do with de- referencing the form. But I don't even know what that means.

This happens even when I open a project that contains
nothing more than an empty form. And reinstalling
VB.NET2003Stand ard did not solve the problem.

Seems to be an error in the project, not in the IDE.

Does this evenoccur when you create a completely new project with a single form (notopening an existing project)? Go into the "bin" folder of yourapplication and start the executable file: Does this throw theexception too? Did you have any beta or trial versions of VS.NETinstalled on the machine?

--
Herfried K. Wagner [MVP]
<http://www.mvps.org/dotnet>
.

xxxxxxxxxxxxxxx xxxxxxx

Herfried: The problem (a "Null Reference" error) occurs
even when I create a completely new project containing
just one form - even if the form is completely blank and
empty. I get the same error msg even when I go into
my "bin" folder and run the ".exe" file. I never had any
beta or trial versions of VB.NET. But I still have Visual
Studio 6 installed on the same PC. Do you have any ideas
on what might be wrong? Paul S. Natanson (Phone [phone]-
0406 9 AM - 9 PM eastern USA time)
pa********@conc entricxxx.netxxx (remove xxxx's from email
address). December 23, 2003

[Armin Zingler]

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

Seems to be an error in the project, not in the IDE.

Does this even

occur when you create a completely new project with a

single form (not

opening an existing project)? Go into the "bin" folder

of your

application and start the executable file: Does this

throw the

exception too? Did you have any beta or trial versions

of VS.NET

installed on the machine?

--
Herfried K. Wagner [MVP]
<http://www.mvps.org/dotnet>
.

xxxxxxxxxxxxxxx xxxxxxx

Herfried: The problem (a "Null Reference" error) occurs
even when I create a completely new project containing
just one form - even if the form is completely blank and
empty. I get the same error msg even when I go into
my "bin" folder and run the ".exe" file. I never had any
beta or trial versions of VB.NET. But I still have Visual
Studio 6 installed on the same PC. Do you have any ideas
on what might be wrong? Paul S. Natanson (Phone [phone]-
0406 9 AM - 9 PM eastern USA time)
pa********@conc entricxxx.netxxx (remove xxxx's from email
address). December 23, 2003

As you say it also happens whenever you start the .exe, it must be a runtime
error. Consequently you should be able to find the error in the IDE, too
(usually). When the error occurs, is there no information _where_ it occurs?
What does the callstack show?
--
Armin

[Paul S. Natanson]

"Armin Zingler" <az*******@free net.de> wrote in message
news:%2******** ********@tk2msf tngp13.phx.gbl. ..

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

Seems to be an error in the project, not in the IDE. Does this even

occur when you create a completely new project with a

single form (not

opening an existing project)? Go into the "bin" folder

of your

application and start the executable file: Does this

throw the

exception too? Did you have any beta or trial versions

of VS.NET

installed on the machine?

--
Herfried K. Wagner [MVP]
<http://www.mvps.org/dotnet>
.

xxxxxxxxxxxxxxx xxxxxxx

Herfried: The problem (a "Null Reference" error) occurs
even when I create a completely new project containing
just one form - even if the form is completely blank and
empty. I get the same error msg even when I go into
my "bin" folder and run the ".exe" file. I never had any
beta or trial versions of VB.NET. But I still have Visual
Studio 6 installed on the same PC. Do you have any ideas
on what might be wrong? Paul S. Natanson (Phone [phone]-
0406 9 AM - 9 PM eastern USA time)
pa********@conc entricxxx.netxxx (remove xxxx's from email
address). December 23, 2003

As you say it also happens whenever you start the .exe, it must be a

runtime error. Consequently you should be able to find the error in the IDE, too
(usually). When the error occurs, is there no information _where_ it occurs? What does the callstack show?
--
Armin

xxxxxxxxxxxxxxx xxxxxxxxxx

Armin: I creatd a brand new project and clicked the start button (before
writing any code). When I click the START button, the form (a blank form)
seems to load OK, but the debugger stops the program and enters BREAK mode
before showing the form.

When the program stops, I get a "Microsoft Development Environment" error
message box that says: "An unhandled exception of type
'System.NullRef erenceException ' occurred in system.windows. forms.dll.
Additional information: Object reference not set to an instance of an
object."

When I view the code in BREAK mode, the word "Form1" in the very first line
code is highlighted. My project has only one form (called "Form1") and it
is entirely completely blank and empty. And my project contains NO
user-written code. All I did was create a new project (called PSN) and
click the start button. The first two lines of code read as follows:

Public Class Form1
Inherits System.Windows. Forms.Form

When the error occurs, the call stack in BREAK mode shows the following:

Name: PSN.exe!PSN.For m1.Main() Line 1 + Ox1d bytes
Language: Basic

PS: I am a novice VB user trying to make the transition from VB6 to VB.NET
and I am very frustrated.

In an effort to debug this, I put a message box in the form load event and
the msg box worked OK. But as soon as I clicked OK in the msg box, I still
got the same Null Reference error.

Got any other ideas?

pa********@conc entricxxx.netxxx (remove xxxx's from email address).
December 24, 2003
Phone [phone]AM-9PM eastern USA time.

[Armin Zingler]

"Paul S. Natanson" <pa*****@concen tric.net> schrieb

Armin: I creatd a brand new project and clicked the start button
(before writing any code). When I click the START button, the form
(a blank form) seems to load OK, but the debugger stops the program
and enters BREAK mode before showing the form.

When the program stops, I get a "Microsoft Development Environment"
error message box that says: "An unhandled exception of type
'System.NullRef erenceException ' occurred in
system.windows. forms.dll. Additional information: Object reference
not set to an instance of an object."

When I view the code in BREAK mode, the word "Form1" in the very
first line code is highlighted. My project has only one form (called
"Form1") and it is entirely completely blank and empty. And my
project contains NO user-written code. All I did was create a new
project (called PSN) and click the start button. The first two lines
of code read as follows:

Public Class Form1
Inherits System.Windows. Forms.Form

When the error occurs, the call stack in BREAK mode shows the
following:

Name: PSN.exe!PSN.For m1.Main() Line 1 + Ox1d bytes
Language: Basic

PS: I am a novice VB user trying to make the transition from VB6 to
VB.NET and I am very frustrated.

In an effort to debug this, I put a message box in the form load
event and the msg box worked OK. But as soon as I clicked OK in the
msg box, I still got the same Null Reference error.

Got any other ideas?

Paul,

in the new project, add this code to your form:

Shared Sub Main
Dim f as new Form1
application.run (f)
end sub

Start again. Does the error still occur?

You also say that Form_Load is reached, so the sub Main you mentioned above
is (perhaps) not the real error location. Could you please run the app again
and post the *full* callstack? Please make the "none user code" (or similar)
visible (by right-clicking in the callstack window and enabling "none user
code").

--
Armin

[Paul S. Natanson]

"Armin Zingler" <az*******@free net.de> wrote in message
news:u9******** ******@TK2MSFTN GP12.phx.gbl...

"Paul S. Natanson" <pa*****@concen tric.net> schrieb

Armin: I creatd a brand new project and clicked the start button
(before writing any code). When I click the START button, the form
(a blank form) seems to load OK, but the debugger stops the program
and enters BREAK mode before showing the form.

When the program stops, I get a "Microsoft Development Environment"
error message box that says: "An unhandled exception of type
'System.NullRef erenceException ' occurred in
system.windows. forms.dll. Additional information: Object reference
not set to an instance of an object."

When I view the code in BREAK mode, the word "Form1" in the very
first line code is highlighted. My project has only one form (called
"Form1") and it is entirely completely blank and empty. And my
project contains NO user-written code. All I did was create a new
project (called PSN) and click the start button. The first two lines
of code read as follows:

Public Class Form1
Inherits System.Windows. Forms.Form

When the error occurs, the call stack in BREAK mode shows the
following:

Name: PSN.exe!PSN.For m1.Main() Line 1 + Ox1d bytes
Language: Basic

PS: I am a novice VB user trying to make the transition from VB6 to
VB.NET and I am very frustrated.

In an effort to debug this, I put a message box in the form load
event and the msg box worked OK. But as soon as I clicked OK in the
msg box, I still got the same Null Reference error.

Got any other ideas?

Paul,

in the new project, add this code to your form:

Shared Sub Main
Dim f as new Form1
application.run (f)
end sub

Start again. Does the error still occur?

You also say that Form_Load is reached, so the sub Main you mentioned

above is (perhaps) not the real error location. Could you please run the app again and post the *full* callstack? Please make the "none user code" (or similar) visible (by right-clicking in the callstack window and enabling "none user
code").

--
Armin

xxxxxxxxxxxxxxx xxxxxxxxxxxxxxx xxxxx

Armin: I added the code that you suggested:

Shared Sub Main
Dim f as new Form1
application.run (f)
end sub

But, after clicking the START button, I still got the same Null Reference
error.

This time, when the error caused my program to enter BREAK mode, the line
that was highlighted was:

Application.Run (f)

And the full callstack (including the non-user code) was as follows:

system.windows. forms.dll!Syste m.Windows.Forms .Control.SetVis ibleCore +
0x139 bytes
system.windows. forms.dll!Syste m.Windows.Forms .Form.SetVisibl eCore + 0xf7
bytes
system.windows. forms.dll!Syste m.Windows.Forms .Control.set_Vi sible + 0x18
bytes

system.windows. forms.dll!Syste m.Windows.Forms .Application.Th readContext.Run M
essageLoopInner + 0x162 bytes

system.windows. forms.dll!Syste m.Windows.Forms .Application.Th readContext.Run M
essageLoop + 0x50 bytes
system.windows. forms.dll!Syste m.Windows.Forms .Application.Ru n + 0x34 bytes
PSN.exe!PSN.For m1.Main() Line 6 + 0x8 bytes Basic

PS: This time, I noticed that when the program entered break mode, a form
entitled Form1 was open. I guess that it had been there yesterday too, but
I never noticed it before because it was hidden behind my code window and
behind the error message.

I also tried adding a button to yesterday's version. But when the form
opens, I get the error before the form is populated with the button.

So, the error appears to be happening after the form loads, but before any
controls are added to it. Is that possible?

Paul S. Natanson pa********@conc entricxxx.netxxx (For real address, just
remove the xxx's.) December 24, 2003 Phone [phone] (9AM-9PM
eastern USA time).

xxxxxxxxxxxxxxx xxxxxxxxxxxxxxx xxx

[Armin Zingler]

"Paul S. Natanson" <pa********@con centricxxx.netx xx (Remove xxx's for
real address.)> schrieb

Armin: I added the code that you suggested:

Shared Sub Main
Dim f as new Form1
application.run (f)
end sub

But, after clicking the START button, I still got the same Null
Reference error.

This time, when the error caused my program to enter BREAK mode, the
line that was highlighted was:

Application.Run (f)

And the full callstack (including the non-user code) was as
follows:
system.windows. forms.dll!Syste m.Windows.Forms .Control.SetVis ibleCore
+ 0x139 bytes
system.windows. forms.dll!Syste m.Windows.Forms .Form.SetVisibl eCore +
0xf7
bytes
system.windows. forms.dll!Syste m.Windows.Forms .Control.set_Vi sible +
0x18
bytes

system.windows. forms.dll!Syste m.Windows.Forms .Application.Th readContext.Run M essageLoopInner + 0x162 bytes

system.windows. forms.dll!Syste m.Windows.Forms .Application.Th readContext.Run M essageLoop + 0x50 bytes
system.windows. forms.dll!Syste m.Windows.Forms .Application.Ru n +
0x34 bytes PSN.exe!PSN.For m1.Main() Line 6 + 0x8 bytes Basic
That's really interesting. I had a look at SetVisibleCore but didn't figure
out what could cause the problem. Um...do you know how to use the
disassembly window? :) I'd single step through the disassembly to find out
what is Nothing within SetVisibleCore.
PS: This time, I noticed that when the program entered break mode, a
form entitled Form1 was open. I guess that it had been there
yesterday too, but I never noticed it before because it was hidden
behind my code window and behind the error message.

I also tried adding a button to yesterday's version. But when the
form opens, I get the error before the form is populated with the
button.

So, the error appears to be happening after the form loads, but
before any controls are added to it. Is that possible?

I guess that the form must have been made visible as you can alredy see it,
so, in Setvisiblecore, I can narrow the problem down to the native
setvisible call - still the sub is quite long.

It is hard for me to find the error. Maybe somebody else remembers the same
error (I think I've heard it before but I am not sure) and has some help for
you. I guess it's an installation (or security (or whatever)) problem.
--
Armin

http://www.plig.net/nnq/nquote.html
http://www.netmeister.org/news/learn2quote.html

[Cor]

Hi Paul,

I don't know the answer either,

But maybe you can make it more visible for you.

Open the designer made region and delete from this row
<System.Diagnos tics.DebuggerSt epThrough()> Private Sub InitializeCompo nent()

<System.Diagnos tics.DebuggerSt epThrough()>

Than push on the F11 function (asuming that it is your step button).

Then maybe it will become more visible.

Cor