Object Reference Error Before Running The Application

  • Thread starter Thread starter Jeff
  • Start date Start date
J

Jeff

I'm getting an Object Reference error before I even run my app, and
I'm not sure where to look to find the cause. I'd appreciate your
help.

When I open my Windows Application project, the following Microsoft
Development Environment error message displays:

"Object reference not set to an instance of an object."

Then when I access the design view of one of my forms, the controls on
the form are hidden behind an error 'display' showing the text at the
end of this post. When I run the app, it seems to run OK. When I
open other projects, I don't get the error, so I'm guessing it's
caused by something in my app. But it would seem that Debug is of no
help, since the error occurs without running the app, and no error
appears when I run the app.

Interesting additional observation: The problem only occurs when I
open the project to a class or module code window (since it was the
active window when I last closed the project). When I open the
project to a design view of a form, the error doesn't appear. Oh, and
I've also tried reinstalling/repairing Visual Studio, and that hasn't
helped. I'm using VB.NET.

Any suggestions???

Thanks for your help.

- Jeff


Here's the error text displayed on the form:

System.NullReferenceException: Object reference not set to an instance
of an object.
at ControlInfoView.Connect.cc1dac46909c42ab()
at ControlInfoView.Connect.dd3392f59d8e3f48(Object e0292b9ed559da7d,
EventArgs fbf34718e704c6bc)
at System.Windows.Forms.Control.OnResize(EventArgs e)
at System.Windows.Forms.Form.OnResize(EventArgs e)
at System.Windows.Forms.Control.OnSizeChanged(EventArgs e)
at System.Windows.Forms.Control.UpdateBounds(Int32 x, Int32 y, Int32
width, Int32 height, Int32 clientWidth, Int32 clientHeight)
at System.Windows.Forms.Control.UpdateBounds()
at System.Windows.Forms.Control.WmMove(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at System.Windows.Forms.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Design.DesignerWindowTarget.DefWndProc(Message&
m)
at System.Windows.Forms.Design.ControlDesigner.DefWndProc(Message& m)
at System.Windows.Forms.Design.ControlDesigner.WndProc(Message& m)
at System.Windows.Forms.Design.ParentControlDesigner.WndProc(Message&
m)
at System.Windows.Forms.Design.ScrollableControlDesigner.WndProc(Message&
m)
at System.Windows.Forms.Design.DocumentDesigner.WndProc(Message& m)
at System.Windows.Forms.Design.FormDocumentDesigner.WndProc(Message&
m)
at System.Windows.Forms.Design.DesignerWindowTarget.OnMessage(Message&
m)
 
* (e-mail address removed) (Jeff) scripsit:
I'm getting an Object Reference error before I even run my app, and
I'm not sure where to look to find the cause. I'd appreciate your
help.
Click to expand...

Post the question to this group:

<
 
Jeff,
I've found this is usually the result of a declaring a class (but not
initiating it), and refering to it in the Load event of the form,
particularly if it inherits from another form

eg
Public Class Form1
.......

Private m_MyObject as MyObject

Private Sub Form_Load(ByVal sender as Object, ByVal e as EventArgs)
Handles MyBase.Load
'Set the value of MyObject or so something with MyObject
End Sub

The problem can be solved if you initialize MyObject when you declare it ,
ie
Private m_MyObject as New MyObject

(Check base classes and make sure you build the project after making the
changes)

Stephen
 
Well, the problem is still occurring, but I've done some additional
testing.

(First, my project doesn't have the type of construct that Stephan
describes in his post. But thanks for the suggestion, Stephan.)

I've distilled the problem down to the MainMenu control. It may occur
with other controls; I just haven't tested beyond this one. I've
re-created the problem by simply creating a new project and adding a
MainMenu control to Form1. Here's what I've done:

1. Start a new Windows Application: (I named mine MenuTest)
(A new project is created, and the IDE opens showing Form1)

2. Add a Main Menu to Form1 by double-clicking the MainMenu control in
the toolbox

3. Save the Project

4. Build the Solution

5. Exit VB.NET

6. Re-Launch VB.NET, open the project

7. View the Design view of Form1

8. Click the MainMenu1 control --> Error!

Microsoft Development Environment
Object reference not set to an instance of an object.

I then added a menu item, saved/built, closed/opened the IDE.
Clicking the MainMenu1 control did NOT raise the error. But if I then
viewed the code window for Form1 and then closed/opened the IDE (so
the code window was displayed as the most recent document), the error
was displayed.

If I delete the suo file and re-open the project, the problem doesn't
occur -- until I next open the project again, when the problem recurs.

I still don't know how to solve the problem! Does anyone have any
suggestions?

- Jeff
 
Well
The windows forms designer has to create an instance of the form and all of the controls in the control collection in order to show it in the designer. Within the constructor of your form, you may be evaluating code which relies on runtime information, causing an error. Sometimes, putting similar code in the LoadEvent of a base form will have the same effect

-Eri
implemental.com
 
Thanks for your response, Eric -

The only code in my simple example is that generated automatically by the
Windows Form Designer. Specifically (after I added the menu item):

Friend WithEvents MainMenu1 As System.Windows.Forms.MainMenu
Friend WithEvents MenuItem1 As System.Windows.Forms.MenuItem

And in Sub InitializeComponent():

Me.MainMenu1 = New System.Windows.Forms.MainMenu
Me.MenuItem1 = New System.Windows.Forms.MenuItem
'
'MainMenu1
'
Me.MainMenu1.MenuItems.AddRange(New System.Windows.Forms.MenuItem()
{Me.MenuItem1})
'
'MenuItem1
'
Me.MenuItem1.Index = 0
Me.MenuItem1.Text = "File"

Me.Menu = Me.MainMenu1


[There is no code in the form's load event -- or elsewhere, for that matter.
All I did was add a mainmenu and a menu item to the default form.]

Any suggestions re how I can solve the problem?? Do you see anything that
would rely on runtime information (as you suggested)?

Thanks again.

- Jeff


Eric Franz said:
Well,
The windows forms designer has to create an instance of the form and all
Click to expand...
of the controls in the control collection in order to show it in the
designer. Within the constructor of your form, you may be evaluating code
which relies on runtime information, causing an error. Sometimes, putting
similar code in the LoadEvent of a base form will have the same effect.
 
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