detecting null -- inetserver asp general

MDW
12/30/2003 9:26:50 AM

As much as I respect Ray, his solution would only work if
ALL the entries were blank. If even one of those had text,
then his test could produce a false positive.

Are you getting this from an HTML form somewhere? If you
are, then another way to do it (call me old fashioned) is
to use client-side script to validate the form entries
before the user even submits the form. Make their browser
do some of the work!

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MDW
12/30/2003 9:48:44 AM

If your client side validation is tight enough, you really
shouldn't need to do much by way of server-side
validation. The only thing I use ASP for is functions that
JavaScript doesn't provide, such as Replace.

If you're worried about people disabling scripting, one
solution I've come up with is this:

<script language="JavaScript">

document.write("<input type=\"submit\"
value=\"Submit\">);

</script>

<noscript>
In order to submit this form, your browser must have
script enabled.
</noscript>
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MDW
12/30/2003 11:35:30 AM

Good point!

Ray, you're fired!
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Michael Walton
12/30/2003 12:14:02 PM

That's how I do it, unfortunately.

Also, are you checking this on the client-side beforehand? It might be a
good idea to do some form validation using Javascript, first, so you save
yourself a trip to the server.

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Ray at <%=sLocation%
12/30/2003 12:16:28 PM

You could concatenate them all:

sStringSum = firstname & surname & address1 & town & county & country &
postcode & phone & email11 & email2 & password1 & password2

If Len(Trim(sStringSum)) = 0 Then
Response.Write "You didn't fill in anything."
Response.End
End If

Ray at work

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Foo Man Chew
12/30/2003 12:18:23 PM

This will only tell you that ALL the fields are empty. (if firstname is
blank *and* surname is blank *and*...)

I usually use client-side validation for this, I have a check for each form
field in JavaScript, and if any field is empty, the form doesn't get
submitted and they're asked to fill in the data. This way, the server
doesn't have to do any work checking, and the user is told immediately
instead of wasting time submitting data and waiting for the server to
respond. You also have an easier time keeping track of the data they've
filled in correctly, because you don't have to re-populate the form if it's
never been submitted.

Of course you check on the server as well, because some people don't allow
JavaScript for some reason. But you can save a lot of time and server
processing by stopping 99% of potential errors at the client.

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Foo Man Chew
12/30/2003 12:20:06 PM

Also, just to save you confusion in the future, null and empty string are
*NOT* the same thing.

\
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Ray at <%=sLocation%
12/30/2003 12:54:04 PM

[quoted text, click to view]

That was how he had his original code setup. I thought about questioning it
but just decided against it. :]

Ray at work

Peter Foti
12/30/2003 12:58:53 PM

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In addition, string concatenation is probably a more expensive operation
than checking the length of each string individually. Sorry Ray, but with
all due respect, I think you fell asleep at the wheel on this one. :)

Regards,
Peter Foti

Ray at <%=sLocation%
12/30/2003 1:12:21 PM

I have yet to wake up this week. :]

Ray at work

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Gav
12/30/2003 5:10:50 PM

Hi,
At the moment i am checking that all the fields have been filled out, at the
moment i am using the following...

if firstname = "" and surname = "" and address1 = "" and town = "" and
county = "" and country = "" and postcode = "" and phone = "" and email11 =
"" and email2 = "" and password1 = "" and password2 = "" then

is there a better more efficient way of doing this??

cheers,
gav

Steven Burn
12/30/2003 5:17:26 PM

'Make sure none of the boxes are empty (zero length)
If len(firstname) = 0 or len(surname) = 0 or len(address1) = 0 or len(town)
= 0 or len(county) = 0 or len(country) = 0 or len(postcode) = 0 or
len(phone) = 0 or len(email11) = 0 or len(email2) = 0 or len(password1) = 0
or len(password2) = 0 Then

Using Len and "Or" instead of "And" is a much better way of doing it.
There's probably also a "cleaner" way of doing it..... I just can't think of
one at the moment.

--
Regards

Steven Burn
Ur I.T. Mate Group
www.it-mate.co.uk

Keeping it FREE!

Disclaimer:
I know I'm probably wrong, I just like taking part ;o)

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Gav
12/30/2003 5:38:53 PM

Hi,
Thanks for all the replies!!! much apreaciated.

I've gone with stevens method, seems to be the tidyest.

As suggested im also going to use a client side check first to reduce the
load on the server

:)

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Steven Burn
12/30/2003 5:46:45 PM

No problem.

--
Regards

Steven Burn
Ur I.T. Mate Group
www.it-mate.co.uk

Keeping it FREE!

Disclaimer:
I know I'm probably wrong, I just like taking part ;o)

[quoted text, click to view]

<aa>
12/30/2003 6:40:44 PM

Detecting Null?

Null is defined as no valid data

If a form field named, say, firstname, is left empty when submitting the
form, then request.form.item("firstname") should return the contents of that
form's field, i.e. a zero-length string, which is valid data, it is not?

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jcochran.nospam NO[at]SPAM naplesgov.com
12/30/2003 8:14:28 PM

On Tue, 30 Dec 2003 17:10:50 -0000, "Gav" <gav1290@ntlworld.com>
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Client side verification would be more appropriate for this I would
think. Besides, I'd just hit a space bar on all the fields so your
code would accept it... :)

Michael D. Kersey
12/30/2003 11:32:52 PM

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Unfortunately it is _impossible_ to write a secure application without
doing server-side validation. A user can _always_ spoof input fields
because the user has complete control of the client side of the
interaction. For example, input may come from not a browser but from a
Perl program that mimics a browser. Such a program can be impossible to
detect.

[quoted text, click to view]

How to spoof the above:
save the HTML page, open it in NotePad, edit out the
<noscript>...</noscript> block, add the <input> fields, save the page
again, load it into the browser and submit the form.

Good Luck,
Michael D. Kersey

TomB
12/31/2003 9:58:22 AM

Nobody mentioned it, so I thought I would....You may want to throw a trim in
there to make sure that your fields aren't all spaces.

firstname = trim(Request.Form("firstname"))

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inetserver asp general : detecting null