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Introduction:

Hey guys, this is the fourth tutorial in the VB programming series. Once again, I have checked and I believe there is no other threads on how to do this.

Tutorial: #4 - Credit Card Validation

Required Materials:

~ VB 2010 or 2008

Features:

We will be making a basic form that will have a masked textbox, that the user will enter their credit card number in, and will be validated through official servers to check if the card is valid. THIS IS NOT A CC DETAIL STEALER!! THIS VERIFIES THROUGH OFFICIAL SERVERS. You might want to let your user know this as well for security reasons.

Video:

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How to do it:

First we are going to create a new WindowsFormApplication, or open an already created one. I am naming mine NGU CC Validator.

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Now once you have done this, you may customize the form and such. You should see something similar to this on your screen:

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Now we are going to add 2 objects, 4 textboxes, and a button. You can place them wherever you want, it doesn't matter. Your form should look something similar to this:

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Now to the coding! We first need to create a private function to check if the credit card number entered is legit or not. We will call this function "ccchecker".

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Code to Copy:

    Private Function ccchecker(ByVal value As String) As Boolean

        Dim checksum As Integer = 0

        Dim doubleflag As Boolean = (value.Length Mod 2 = 0)

        Dim ccnumber As Char

        Dim ccnumbervalue As Integer



        For Each ccnumber In value

            ccnumbervalue = Integer.Parse(ccnumber)

            If doubleflag Then

                ccnumbervalue *= 2

                If ccnumbervalue > 9 Then

                    ccnumbervalue -= 9

                End If

            End If

            checksum += ccnumbervalue

            doubleflag = Not doubleflag

        Next

        Return (checksum Mod 10 = 0)

    End Function

Now we must link the button to check this function with the number provided. This is fairly simple to do, as you will see.

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Code To Copy:

    If ccchecker(TextBox1.Text & TextBox2.Text & TextBox3.Text & TextBox4.Text) Then

            MsgBox("This card has been validated as a correct card number!", MsgBoxStyle.Information)

        Else

            MsgBox("This card has been validated as an incorrect card number", MsgBoxStyle.Critical)

        End If

We are done! If you enter an incorrect card number, you should see a popup like this:

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If you enter a correct card number, you should see a popup like this:

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Have a good Wednesday NGU.

im using this at the moment thanks