[RESOLVED] [Access 2002] Null evaluating to true in opposite comparisons

[sevenhalo]

I have the following code:

Private Sub Form_Load()
    If Me.OpenArgs = Null Then       
        DoCmd.GoToRecord , , acNewRec
    Else                               
            'Do something else
    End If
End Sub

Everytime I step through it, it drops to the else clause. If I flip the comparison to:

Private Sub Form_Load()
    If Me.OpenArgs <> Null Then       
        DoCmd.GoToRecord , , acNewRec
    Else                               
            'Do something else            
    End If
End Sub

It still drops to the else clause. I checked the value of Me.OpenArgs to see what it actually is:


What am I doing wrong here? How can it not be either true or false?

My first thought was that Null is only used to compare objects (like in VB.Net), but the immediate value told me otherwise.

Thanks!

[RobDog888]

Null is an unknown value so it can not be evaluated at all. There are the IsNull and other null comparison functions. It just depends on your situation.

IsNull, IsEmpty, NullIf, nz, NullString are all possibilities.

What is OpenArgs data type?

[sevenhalo]

String I would assume? It's just the opening arguements you pass to the access form. It's built in (I didn't create it).

[RobDog888]

Close but no cigar!

Determines the string expression specified by the OpenArgs argument of the OpenForm method that opened a form. Read/write Variant.

Private Sub Form_Load()
    Dim strArgs As String
    strArgs = vbNullString 'Initialize var
    strArgs = Me.OpenArgs
    If Len(strArgs) > 0 Then
        'Args passed
    Else
        'No args passed
    End if
End Sub

[sevenhalo]

Doh!

I'll give it a shot tomorrow. Thanks.

[sevenhalo]

Ok, I gave it a shot with the following:

Private Sub Form_Load()
    Dim strArgs As String
    strArgs = vbNullString 'Initialize var
    [HL]strArgs = Me.OpenArgs[/HL]
 
    If Len(strArgs) = 0 Then       
        DoCmd.GoToRecord , , acNewRec
    Else                               
            
    End If
End Sub

It breaks on the highlighted line with an "Invalid use of null" error.

BUT!!!
Using the other suggesition you offered (IsNull), I was able to evaluate that.

Thanks Rob

[westconn1]

try

if not isnull(me.openargs) then strargs = me.Openargs

pete

[RobDog888]

Or using and IIF with an IsNull in it would work too.

strArgs = IIf(IsNull(Me.OpenArgs) = True, vbNullString, Me.OpenArgs)