Checking Null values

[josh2009]

newbie here. Trying to check for nulls using the ff-

if currentCathRecord("Account_Number") Is Nothing Then
MessageBox.Show("Please enter Account Number or else ...")
return
End If

Nothing happens. No errors but message is not displayed. Field is defined as varchar(25) is SQL. Any help will be greatly appreciated. Thanks.

 

[JuggaloBrotha]

If this is coming from a DB then you use DBNull.Value when checking for null's:

If currentCathRecord("Account_Number") Is DBNull.Value Then
    MessageBox.Show("Please enter Account Number or else ...")
Else
    'Rest of program
End If

 

[josh2009]

Thanks for the quick reply. Let me try it out and will let you know. Thanks.

 

[josh2009]

Thanks again for the help. It worked great for me. One other question, if I want to check for the opposite, field is populated, how do I use the dbnull.value? I tried -

if currentCathRecord("Account_Number") Is Not DBNull.Value Then
		MessageBox.Show("Account Number populated.")
		bFlag=False
		return
	End If

I got an error message. Thanks.

 

[JuggaloBrotha]

Thanks again for the help. It worked great for me. One other question, if I want to check for the opposite, field is populated, how do I use the dbnull.value? I tried -

if currentCathRecord("Account_Number") Is Not DBNull.Value Then
		MessageBox.Show("Account Number populated.")
		bFlag=False
		return
	End If

I got an error message. Thanks.

If currentCathRecord("Account_Number") IsNot DBNull.Value Then
    MessageBox.Show("Account Number populated.")
    bFlag=False
    return
End If

or

If Not (currentCathRecord("Account_Number") Is DBNull.Value) Then
    MessageBox.Show("Account Number populated.")
    bFlag=False
    return
End If

 

[josh2009]

Excellent! That worked great for me. Thanks again for all your help.

 

[bdinnocenzo]

I have a couple of short functions that test for DBNull and was wondering if this is a good approach or not? Typically I'll read data and store it in a variable of a particular type...integer, string, decimal, etc. So I wrote a couple of short functions to make the overall code read better. Here's an example:

    Private Function ToBool(ByVal thing As Object, _
                         Optional ByVal rValue As Boolean = False) As Boolean
        If thing IsNot DBNull.Value Then
            Return CBool(thing)
        Else
            Return rValue
        End If
    End Function

Then I call it like this:

                    .IncludeNote = ToBool(dr("IncludeNote"))
                    .LiveItem = ToBool(dr("LiveItem"))
                    .Priceless = ToBool(dr("Priceless"))
                    .Active = ToBool(dr("Active"), True)

Makes sense? Is this a good way to deal with nulls?