onLost焦点事件不起作用-ms访问

Question

This code is not working. Can anyone help me out?

Private Sub txtErrorComment_5_LostFocus()

    If IsEmpty(Me.txtErrorComment_5) Then
        MsgBox "Eh..! It cannot be Empty."
    End If

End Sub

Answer 1

txtErrorComment_5 is probably Null - which evaluates to False when run through IsEmpty() - yes, this is un-intuitive, but whenever you compare to Null, the result is false.

Try the following:

Private Sub txtErrorComment_5_LostFocus()

    If IsEmpty(Me.txtErrorComment_5) or IsNull(Me.txtErrorComment_5) Then
        MsgBox "Eh..! It cannot be Empty."
    End If

End Sub

Or just:

Private Sub txtErrorComment_5_LostFocus()

    If IsNull(Me.txtErrorComment_5) Then
        MsgBox "Eh..! It cannot be Empty."
    End If

End Sub

IsNull can handle Null's

Edit:

@David-W-Fenton is correct. The better way to do this BeforeUpdate (not LostFocus)

Private Sub txtErrorComment_5_BeforeUpdate(Cancel As Integer)

     If IsNull(Me.txtErrorComment_5) Then
         MsgBox "Eh..! It cannot be Empty."
         Cancel=true
     End If

End Sub

Answer 2

To detect whether txtErrorComment_5 is blank, concatenate a Null string to its value and see whether the character length of the combined expression is zero.

Private Sub txtErrorComment_5_LostFocus()
    If Len(Me.txtErrorComment_5 & vbNullString) = 0 Then
        MsgBox "Eh..! It cannot be Empty."
    End If
End Sub

If you want txtErrorComment_5 treated as blank when it contains only one or more space characters, include the Trim() function.

Private Sub txtErrorComment_5_LostFocus()
    If Len(Trim(Me.txtErrorComment_5) & vbNullString) = 0 Then
        MsgBox "Eh..! It cannot be Empty."
    End If
End Sub