If Not IsNull in ASP Classic - vbscript

Question

I'm fairly new to asp and I've got a syntax error I would like help on if you can.
I've got an ASP page that shows a table that pulls data from sql. Most of the data hasn't been populated yet so returns a NULL. The data type in question is numeric. I need to FormatNumber the rs when it is not null and not populate if it is.
This is what I have
<%=If Not IsNull(rs("ContractValue")) Then FormatNumber(rs("ContractValue"),0) end if%>
But as mentioned, im getting a syntax error.
What am i doing wrong?

Answer 1

I would recommend not using IsNull() in this scenario, but to answer the question about the syntax error first.
The reason is the <%= %> syntax which is shorthand for
<% Response.Write %>
in Classic ASP.
So what you are actually doing if written without the shorthand approach is;
<% Response.Write If Not IsNull(rs("ContractValue")) Then FormatNumber(rs("ContractValue"),0) End If %>
which is incorrect syntax and will trigger a Syntax Error.
To fix the code remove the = from the <% %> tags, like so;
<% If Not IsNull(rs("ContractValue")) Then Response.Write FormatNumber(rs("ContractValue"),0) End If %>
What about using IsNull?
While this can work it can often give weird results because a DBNull (depending on the database being used) can be different and is often different to the VBScript vbNull variant.
Because of this and the fact VBScript isn't strongly typed I find it useful to use a simple quick cast to string to avoid Nulls then check for valid data.
Example numeric check
Dim contractValue
contractValue = rs("ContractValue") & ""
If Len(contractValue) > 0 And IsNumeric(contractValue) Then contractValue = Clng(contractValue) Else contractValue = 0
You can take this further by writing a reusable piece of code that IIf() function explained in this post.
How to do a single line If statement in VBScript for Classic-ASP? (Mentioned by #TasosK in the comments)
Something like this;
Dim contractValue
contractValue = rs("ContractValue") & ""
contractValue = IIf(Len(contractValue) > 0 And IsNumeric(contractValue), contractValue, 0)
#Paul made a good point about evaluation of parameters, in the original code would potentially break
contractValue = IIf(Len(contractValue) > 0 And IsNumeric(contractValue), Clng(contractValue), 0)
because Clng(contractValue) would be evaluated regardless of whether the outcome was True or False. So any formatting would need to be afterwards or a more complex version of the IIf() function be built.

Answer 2

If Not IsNull(rs("ContractValue")) Then
<%=FormatNumber(rs("ContractValue"),0)%>
end if
Do not be in a hurry with Classic ASP.
I'm sure you want to insert content in between some HTML code which made you bunch up all that code. If that is the case, I suggest you separate VBscript code from HTML like below for example;
<%
Dim valueToOutput
If Not IsNull(rs("ContractValue")) Then
valueToOutput=FormatNumber(rs("ContractValue"),0)
end if
%>
<!-- HTML Code continues below with an inserted VBscript variable -->
There are a total of <%=valueToOutput%> oranges available!

Answer 3

If dealing with too many null fields, the code will be riddled with too many IF-THEN-ELSE statements and that would look really ugly.
Consider using the COALESCE function on the database side, so the field values don't come up as null on the recordset, or alternatively, consider using your own coalesce function in ASP that you can use over and over again.
Function Coalesce(inputValue, replaceWith)
if isnull(X) then
Coalesce = replaceWith
else
Coalesce = inputValue
end if
End Function
Then you can use something like this:
<%=FormatNumber(Coalesce(rs("ContractValue"),0),0)%>