# ASP Credit Card Validation

**URL:** <https://forum.kirupa.com/t/asp-credit-card-validation/214278>\
**Category:** programming\
**Created:** [January 26, 2007, 10:27pm UTC](https://forum.kirupa.com/t/asp-credit-card-validation/214278 "2007-01-26T22:27:19Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![dude9er](https://avatars.discourse-cdn.com/v4/letter/d/4af34b/32.png) [@dude9er](https://forum.kirupa.com/u/dude9er)\
**Post date:** [January 26, 2007, 10:27pm UTC](https://forum.kirupa.com/t/asp-credit-card-validation/214278/1 "2007-01-26T22:27:19Z")

</div>

I’m trying to merge my credit card validation with the below Luhn Algorithm validation

```auto

function CheckCC(CC_NUM)
Dim i, w, x, y

InputError=0
CC_NUM = Replace(Replace(Replace(CStr(CC_NUM), "-", ""), " ", ""), ".", "")
y = 0
'Process digits from right to left, drop last digit if total length is even
w = 2 * (Len(CC_NUM) Mod 2)
For i = Len(CC_NUM) - 1 To 1 Step -1
x = Mid(CC_NUM, i, 1)
if IsNumeric(x) Then
Select Case (i Mod 2) + w
Case 0, 3 'Even Digit - Odd where total length is odd (eg. Visa vs. Amx)
y = y + CInt(x)
Case 1, 2 'Odd Digit - Even where total length is odd (eg. Visa vs. Amx)
x = CInt(x) * 2
if x > 9 Then
'Break the digits (eg. 19 becomes 1 + 9)
y = y + (x \ 10) + (x - 10)
Else
y = y + x
End if
End Select
End if
Next

'Return the 10's complement of the total    
y = 10 - (y Mod 10)
if y > 9 Then y = 0
CheckCC = (CStr(y) = Right(CC_NUM, 1))

End function

```

The code I have been using works great and allows for InputErrors in hidden fields. I want to try and merge the two and allow the above Luhn validation to target textField “CC\_NUM” and place a response error into hidden field “Reason” if the crdit card is bad.

When the above function is called, how do I incorporate an error to tell the user that the credit card is invalid?

Here is my code:

```auto

dim InputError,Reason,Reason2,Reason3

InputError=0
'check for numeric vals in str
'if no pass test, no need to continue proc
If Not IsNumeric(CC_NUM) Then
	Reason = "<strong>ERROR:</strong> Card Number contains invalid characters. Use Numbers ONLY without hyphens or spaces."
	InputError=InputError+1
ELSE
if CC_TYPE = "AMEX" AND Len(CC_NUM) <> 15 THEN
	Reason = "<strong>ERROR:</strong> AMEX Number is " & Len(CC_NUM) & " Digits Long instead of 15."
		InputError=InputError+1
	      else
	if CC_TYPE = "VISA" AND Len(CC_NUM) = 13 Or Len(CC_NUM) = 16 THEN
	      Else
	InputError=InputError+1
	Reason = "<strong>ERROR:</strong> Visa Card Number is " & Len(CC_NUM) & " Digits Long instead of 13 or 16."
	InputError=InputError+1
		end if	
	if CC_TYPE = "MasterCard" AND Len(CC_NUM) <> 16 THEN
	Reason = "<strong>ERROR:</strong> MasterCard Number is " & Len(CC_NUM) & " Digits Long instead of 16."
	InputError=InputError+1
		end if
		'===============================================
if CC_TYPE = "AMEX" AND Len(SecCode) <> 4 THEN
	Reason3 = "<strong>ERROR:</strong> AMEX Security Code should contain <strong>4 </strong>Digits."
	InputError=InputError+1
end if

if CC_TYPE = "VISA" AND Len(SecCode) <> 3 THEN
	Reason3 = "<strong>ERROR:</strong> Visa Security Code should contain <strong>3 </strong>Digits."
	InputError=InputError+1
end if

if CC_TYPE = "MasterCard" AND Len(SecCode) <> 3 THEN
	Reason3 = "<strong>ERROR:</strong> MasterCard Security Code should contain <strong>3</strong> Digits."
	InputError=InputError+1
end if

End if
end if

```

Thanks everyone in advance!!