Senin, 10 April 2017

Re: [MS_AccessPros] Invalid use of Null

 

Hi John,


Yes! I have applied your code and is working, i don't need to display a message.

Thank you very much.
Regards,
Khalid


---In MS_Access_Professionals@yahoogroups.com, <JohnV@...> wrote :

Khalid-

Use On Error Resume Next if it's likely your code will trigger an error, but you don't care about just ignoring it.  If you're happy leaving the rate 0 if the DLookup fails, then use that.  Note that you can still check for Err <> 0 right after a statement that might fail to see if an error was triggered but ignored.

As for the code I suggested to avoid any error, you could do something like a MsgBox to the user to let them know that you're unable to set the rate for them, then simply Exit Sub.

John Viescas, Author
Effective SQL
SQL Queries for Mere Mortals 
Microsoft Access 2010 Inside Out
Microsoft Access 2007 Inside Out
Microsoft Access 2003 Inside Out
Building Microsoft Access Applications 
http://www.viescas.com/ 
(Paris, France)




On Apr 10, 2017, at 1:04 AM, khalidtanweerburrah@... [MS_Access_Professionals] <MS_Access_Professionals@yahoogroups.com> wrote:



Hi John,

Thanks for answering.

Actually my question was simply to know that my code is working and giving me no error on getting Focus to the control "Rate", whether it is correct or there is some other method or way to define the code, particularly the line:
==> On Error Resume Next 

The event is as follows:

Private Sub Rate_GotFocus()
On Error Resume Next
    
    If IsNull(WeightOfCarton) Then
        MsgBox "Oops you forget to enter Weight Of Carton." & vbCrLf & _
        "Please enter Gross Weight." _
        , vbExclamation, "Missing Entry"
        WeightOfCarton.SetFocus
    End If
    
    Dim varRate As Double
    varRate = DLookup("DestinationRate", "tblDestinationRates", _
              "Destination = '" & Me.cmbDestination & _
              "' AND ProductID = " & Me.ProductID & "")
              Me.Rate = Nz(varRate, 0)
End Sub

I did tried with the code you suggested to see the results, but i'm sorry i don't know what should be written On Error Statement ?

Also please see first para of my this reply, i needed answer for that. Even if you suggest to use your code then please tell me what should be the On Error statement. Sorry for my limited knowledge.

Regards,
Khalid



---In MS_Access_Professionals@yahoogroups.com, <JohnV@...> wrote :

Khalid-

You can test for empty entries like this (right after the On Error statement):

    If (Len(Me.cmbDestination & "") = 0) Or (Len(Me.ProductID & "") = 0 Then
        ' Take alternative action - don't try to lookup the rate

    Else
        varRate = DLookup( ….
        Me.Rate = NZ(varRate, 0)
    End If


John Viescas, Author
Effective SQL
SQL Queries for Mere Mortals 
Microsoft Access 2010 Inside Out
Microsoft Access 2007 Inside Out
Microsoft Access 2003 Inside Out
Building Microsoft Access Applications 
http://www.viescas.com/ 
(Paris, France)




On Apr 9, 2017, at 7:02 PM, khalidtanweerburrah@... [MS_Access_Professionals] <MS_Access_Professionals@yahoogroups.com> wrote:









------------------------------

Hi John,


I have a Form "New Cargo Collection Input" on its sub form "NewCargoCollectionInputsubform".

This sub form has a Text box "Rate" -->Standard, Decimal Places--> 2 on its On Got Focus event i 

have this code:


Private Sub Rate_GotFocus()

On Error Resume Next

    

    Dim varRate As Double

    varRate = DLookup("DestinationRate", "tblDestinationRates", _

              "Destination = '" & Me.cmbDestination & _

              "' AND ProductID = " & Me.ProductID & "")

              Me.Rate = Nz(varRate, 0)

End Sub


The issue is that if i omit the line "On Error Resume Next" i get an error message

Run-time error '94' Invalid use of Null


This happens when in "tblDestinationRates" there is no entry for Destination and ProductID

which is selected in sub form.


There is a form "Add New Destination Freight Rates" in which "DestinationRate" are entered for a 

specific Destination and ProductID when needed.


I need to know that is putting the line "On Error Resume Next" correct approach and logic ?

In this case, if there is no entry for Destination and ProductID. Text Box "Rate" shows 0.00 value 

and user enters value of his choice, else it picks the value from tblDestinationRates


Regards,

Khalid










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