I was looking at different ways of doing the same thing and at the moment
was looking at the use of "is" and "=", as I have at times found that I will
do something like

if something = 0

and will get an error that says I can't use "=" (or <>) in this case case I
must use "is" ( or not something is).  I am trying to find out when this is
the case - when I can use the "=" and when I have to use "is.

For example, I have a small piece of code checking for the existance of a
session cookie:

if session("tom") = nothing then
trace.warn("Tom not there")
trace.warn("Len(session('Tom')) = " & Len(session("Tom")))
if len(session("Tom")) = 0 then
 trace.warn("also got a hit on <> 0")
end if
end if

This can also be run as:

if session("tom") is nothing then
trace.warn("Tom not there")
trace.warn("Len(session('Tom')) = " & Len(session("Tom")))
if len(session("Tom")) = 0 then
 trace.warn("also got a hit on <> 0")
end if
end if

So 'session("Tom") = nothing' and 'session("Tom") is nothing' as well as
'Len(session("Tom"))' are all equivalent.

Not sure if there is a best way or just whatever strikes you fancy.

I do know that in some cases you can't use the "=" and  must use "is".  I
just don't know why in some cases you can use both (or all 3 ways) and in
some cases you must us "is".

Can someone help me out on the difference?

Thanks,

Tom