How does the IsNull work??

[josie]

I am trying to capture the value of a checkbox on the current report.
I am using the IsNull to try and get around a "Runtime error: 2427 You entered an expression that has no value"
when I use the code;

varPaid = Me!Paid

I am assuming I get this error because sometimes the checkbox isn't ticked??

Anyway, I thought I had it now but the msgbox to get the checkbox value always returns a false - even when the checkbox is ticked.

The code I am using is;

Private Sub Report_Open(Cancel As Integer)
Dim varPaid As Boolean
'check the value
MsgBox varPaid

varPaid = IsNull(Me!Paid)
'check the value again
MsgBox varPaid

If varPaid = False Then
Me.LblPaid.Visible = False
Else
Me.LblPaid.Visible = True
'Me.Section(4).Visible = True

End If

End Sub

What am I not getting (ok, all of it I hear u say <grin>.
josie

 

[ErikSnoek]

That is because the checkbox value is only null when no value has been specified. One of the many solutions to your current problem would be using:
varPaid = IIf(IsNull(Me!Paid), False, Me!Paid)

 

[chergh]

Try moving your code to the reports "on_format" event.

 

[josie]

Hmmm....
that doesn't seem to want to work. I get the logic, if me.paid is null then make it false else make it whatever me.paid is.
But now I am back to the original error of "Expression that has no value"
I put the code you suggested as a replacement to the
varPaid = IsNull(Me!Paid)
line - was that what I was supposed to do?
josie

 

[josie]

Um - can't seem to find the report on_format event.
I've got on open, close, activate, deactive, no data, page & error.
Am I going mad??
josie

 

[chergh]

I think the issue is that it has no value on the "report_open" event. Move your code to the "on_format" event and see what happens.

The "on_format" event can be found by pulling up the properties in the detail section of the report.

 

[josie]

thanks forum buddies!
between the alternate iif statement and the move the report I pulled it together.
The code needed to go on the on_activate event to work as I am setting filter criteria from another form.
But the feedback pointed me in exactly the right direction.
much appreciated
josie

 

[gemma-the-husky]

if you have a form with no data (say its a form that doesnt allow additions, but has no data) then everything on the form is UNDEFINED rather then just NULL

if you then try to do a

if nz(somefield,0) this fails because somefield is undefined

you can still error trap it etc, but its not obvious what is happening until youve seen it once.