Validate on a maskedtextbox

Public Class Form1
	Private Sub OnMaskInputRejected(sender As Object, e As MaskInputRejectedEventArgs) Handles MaskedTextBox1.MaskInputRejected
		MessageBox.Show(String.Format("{0} was rejected; {1}", e.Position, e.RejectionHint))
	End Sub

	Private Sub OnTypeValidationCompleted(sender As Object, e As TypeValidationEventArgs) Handles MaskedTextBox1.TypeValidationCompleted
		If e.IsValidInput Then
			If e.ReturnValue.ToString().Length < 16 Then
				MessageBox.Show("The entered card number must contain 16 digits.")
				e.Cancel = True
			ElseIf Not e.ReturnValue.ToString().LuhnValidation() Then
				MessageBox.Show("Entered card number is invalid.  Failed Luhn.")
				e.Cancel = True
			End If
		Else
			MessageBox.Show("The entered card number must contain 16 digits.")
			e.Cancel = True
		End If
	End Sub
End Class

Module Extensions
	<System.Runtime.CompilerServices.Extension()> _
	Public Function LuhnValidation(ByVal source As String) As Boolean
		Dim result As Boolean = False
		Try
			' We should validate that we are dealing with integers.
			If source.All(Function(c) Char.IsNumber(c)) Then
				' Rules of algorithm
				' 1.  Reverse the order of the digits in the number.
				' 2.  Take the first, third, ... and every other odd digit in the reversed digits and sum them to form the partial sum s1
				' 3.  Taking the second, fourth ... and every other even digit in the reversed digits:
				'     a.  Multiply each digit by two and sum the digits if the answer is greater than nine to form partial sums for the even digits
				'     b.  Sum the partial sums of the even digits to form s2
				' 4.  If s1 + s2 ends in zero then the original number is in the form of a valid credit card number as verified by the Luhn test.
				' Code from - http://rosettacode.org/wiki/Luhn_test_of_credit_card_numbers#Visual_Basic_.NET
				result = source.Select(Function(c, i) (AscW(c) - 48) << ((source.Length - i - 1) And 1)).Sum(Function(n) If(n > 9, n - 9, n)) Mod 10 = 0
			End If
		Catch ex As Exception
			result = False
		End Try
		Return result
	End Function
End Module

Select allOpen in new window

 Public Function LuhnValidation(ByVal source As String) As Boolean
        Dim result As Boolean = False
        Try
            ' We should validate that we are dealing with integers.
			If source.All(Function(c) Char.IsNumber(c)) Then
                ' Rules of algorithm
                ' 1.  Reverse the order of the digits in the number.
                ' 2.  Take the first, third, ... and every other odd digit in the reversed digits and sum them to form the partial sum s1
                ' 3.  Taking the second, fourth ... and every other even digit in the reversed digits:
                '     a.  Multiply each digit by two and sum the digits if the answer is greater than nine to form partial sums for the even digits
                '     b.  Sum the partial sums of the even digits to form s2
                ' 4.  If s1 + s2 ends in zero then the original number is in the form of a valid credit card number as verified by the Luhn test.
                ' Code from - http://rosettacode.org/wiki/Luhn_test_of_credit_card_numbers#Visual_Basic_.NET
				result = source.Select(Function(c, i) (AscW(c) - 48) << ((source.Length - i - 1) And 1)).Sum(Function(n) If(n > 9, n - 9, n)) Mod 10 = 0
            End If
        Catch ex As Exception
            result = False
        End Try
        Return result
    End Function

Select allOpen in new window

1. Right click on your project and choose properties -[b]or[/b]- Choose '[b]Project[/b]' -> '[b]<project name> Properties[/b]' from the menu.

2. Select the '[b]Compile[/b]' tab.

3. Press (or click) the '[b]Advanced Compile Options...[/b]' button.

4. Look at the selected '[b]Target framework (all configurations):[/b]' drop down.

Private Function LuhnValidation(ByVal source As String) As Boolean
	Dim result As Boolean = False
	Try
		' We should validate that we are dealing with integers.
		If Not IsNumeric(source) Then Exit Function

		' Rules of algorithm
		' 1.  Reverse the order of the digits in the number.
		' 2.  Take the first, third, ... and every other odd digit in the reversed digits and sum them to form the partial sum s1
		' 3.  Taking the second, fourth ... and every other even digit in the reversed digits:
		'     a.  Multiply each digit by two and sum the digits if the answer is greater than nine to form partial sums for the even digits
		'     b.  Sum the partial sums of the even digits to form s2
		' 4.  If s1 + s2 ends in zero then the original number is in the form of a valid credit card number as verified by the Luhn test.
		Dim sum As Integer = 0
		For i As Integer = source.Length - 1 To 0 Step -1
			If i Mod 2 <> 0 Then
				sum = sum + (AscW(source(i)) - 48)
			Else
				If ((AscW(source(i)) - 48) * 2) > 9 Then
					sum = sum + ((((AscW(source(i)) - 48) * 2) \ 10) + (((AscW(source(i)) - 48) * 2) - 10))
				Else
					sum = sum + ((AscW(source(i)) - 48) * 2)
				End If
			End If
		Next
		result = sum Mod 10 = 0
	Catch ex As Exception
		result = False
	End Try
	Return result
End Function

Select allOpen in new window