Examining content of a text box

[GraeagleBill]

I have a text box that has as its ControlSource:

=DSum("Debit","QSelects","[bxHighlight]=True")

Since DSum returns Null if no records are returned, ought not the TB be Null as well?

        If IsNull(Me.tbTotalDeb3HLt) Then    'Any highlighted transactions?

Apparently not? Nor, is it Empty and also not zero. Other tests, like what is its Value property result in error "You entered an expression that has no value".

I realize I could solve this by simply running the ControlSource DSum in code to test for its value, but what's the fun in that?

So, what should the test statement be?

[Welshgasman]

Or just use he NZ() function?

[GraeagleBill]

If you mean this:

If Nz(Me.tbTotalDeb3HLt) = 0 Then

Then no, error "You entered an expression that has no value"

[Welshgasman]

No, NZ() the DSum()

[GraeagleBill]

Like I indicated in my OP that running the DSum in code works fine, but why/how to examine the vale of the TB bound to the DSum.

If IsNull(DSum("Debit", "QSelects", "[bxHighlight]=True")) Then

[Welshgasman]

Hmm,

I added a textbox control with source of

=DSum("Amount","TestTransactions","ID=0")

Then added

Private Sub cmdTest_Click()
If IsNull(Me.TxtDsum) Then
    MsgBox "Null"
Else
    MsgBox "Not Null"
End If
End Sub

and I get null.?

Change the ID to 2 (which does exist) I get the amount and I get Not Null

So no idea why it does not work for you?

[GraeagleBill]

Likewise! My original code was exactly as you've coded in your example and posted in the OP. Why the DSum return doesn't propagate the current value of the TB only leaves be to believe that perhaps a few copy/paste operations during report design view left a few TB's corrupted?

[ArviLaanemets]

If you mean this:

If Nz(Me.tbTotalDeb3HLt) = 0 Then

Then no, error "You entered an expression that has no value"

This will always return False for you, as default second parameter for Nz() is an empty STRING!
Instead you must use Nz(Me.tbTotalDeb3HLt,0)

[Micron]

as default second parameter for Nz() is an empty STRING!

Only when Nz is used in a query; otherwise the return data type is decided by the whether the context determines it should be Null or ZLS.

The DSum function should return Null if there are no records that satisfy the criteria so not sure why a test for Null would not result in Null unless you're summing numbers that are text data type. Here's some tests I did with a calculated textbox on a form and directly on the table. Note: not my db so don't mind the wonky names.

TABLE
?DSum("[Point Value]","[Attendance Log]","EmployeeID=1234")
4
?TypeName(DSum("[Point Value]","[Attendance Log]","EmployeeID=1234"))
Double
?DSum("[Point Value]","[Attendance Log]","EmployeeID=123") << no such record with 123
Null

TEXTBOX (with criteria 123)
?TypeName(forms![Attendance Log1].Text175.value)
Null