Making a Startup Windows Form Invisible

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Roger Stenson - 26 Feb 2005 22:33 GMT

' Hi all
I have been using the following example from the Dot Net Help screen with
the above title as my model

Sub Main()

' Instantiate a new instance of Form1.

Dim f1 as New Form1()

' Customize the form.

f1.Text = "Running Form"

' Show the instance of the form modally.

f1.ShowDialog()

End Sub

My Code in Sub Main reads as follows

Dim Signon =As New frmSignon(_populatelastlogon) Executes ok

Signon.lstOrganisation.Items.Add("Anything") System Crashes -
message below

Signon.ShowDialog()

This and any other attempt to address the members of the List Box
lstOrganisation results in the following error message

"A unhandled exception of type 'System.NullReferenceException' occurred in
BRUserInterface.exe

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

A quick watch on the control produces a value of Nothing

I would be grateful if some one would tell me how to deal with this issue

Roger Stenson

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Joergen Bech <jbech<NOSPAM>@ - 27 Feb 2005 07:52 GMT

This line suggests that you have created your own constructor for the
form:

>Dim Signon =As New frmSignon(_populatelastlogon) Executes ok

e.g. something like:

Public Sub New()
MyBase.New()

'This call is required by the Windows Form Designer.
InitializeComponent()

'Add any initialization after the InitializeComponent() call

End Sub

Public Sub New(ByVal blnTest As Boolean)
MyBase.New()
'Do nothing
End Sub

where calling the custom constructor does not result in a call
to InitializeComponent, which is where your listbox is created.

The fact that the "Text" property can be set in the example
you are working from is because the Form class is derived
from the Control one, which contains a Text property.

But as you did not supply the code for the constructor for
frmSignon(<something>), this is just speculation.

/JB

>' Hi all
>I have been using the following example from the Dot Net Help screen with
[quoted text clipped - 39 lines]
>
>Roger Stenson

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Roger Stenson - 27 Feb 2005 18:13 GMT

Hi Joergen
Thank you for your advice and the speed of its delivery. You not only solved
my problem but also persuaded me to read the advanced sections of the text I
am using to convert from VB6 to .Dot Net. I now more fully understand the
context of your remarks and the differences between the two.
Roger Stenson

> This line suggests that you have created your own constructor for the
> form:
[quoted text clipped - 73 lines]
>>
>>Roger Stenson

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Making a Startup Windows Form Invisible

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