How to check if a POST submitted field exists in VBScript?

Question

After a form is submitted, how does one check server-side if a particular field exists? For example:

If [Exists] Request(\"FieldName\") Then
    ...
End If
<         


        

Answer 1

To check if the parameter was present (without caring about its value) it is also possible to write:

fieldValue = Request("FieldName")
if Not IsEmpty(fieldValue) ...

One advantage over Count method above is, that you can test the variable, without referring to the field name again. Advantage over testing for "" is that if you pass &FieldName without assigning value, test for "" will yield true, but IsEmpty returns false.

Edit: Turns out this is not reliable in IIS.

1. For the url with ?param alone, or ?param=¶m2, IsEmpty(param) returns false, but
2. For the url with ?param¶m2, IsEmpty(param) weirdly returns true ...