''' <summary>Determines if a password is sufficiently complex.</summary>
''' <param name="pwd">Password to validate</param>
''' <param name="minLength">Minimum number of password characters.</param>
''' <param name="numUpper">Minimum number of uppercase characters.</param>
''' <param name="numLower">Minimum number of lowercase characters.</param>
''' <param name="numNumbers">Minimum number of numeric characters.</param>
''' <param name="numSpecial">Minimum number of special characters.</param>
''' <returns>True if the password is sufficiently complex.</returns>
Function ValidatePassword(ByVal pwd As String, _
Optional ByVal minLength As Integer = 8, _
Optional ByVal numUpper As Integer = 2, _
Optional ByVal numLower As Integer = 2, _
Optional ByVal numNumbers As Integer = 2, _
Optional ByVal numSpecial As Integer = 2) _
As Boolean
' Replace [A-Z] with \p{Lu}, to allow for Unicode uppercase letters.
Dim upper As New System.Text.RegularExpressions.Regex("[A-Z]")
Dim lower As New System.Text.RegularExpressions.Regex("[a-z]")
Dim number As New System.Text.RegularExpressions.Regex("[0-9]")
' Special is "none of the above".
Dim special As New System.Text.RegularExpressions.Regex("[^a-zA-Z0-9]")
' Check the length.
If Len(pwd) < minLength Then Return False
' Check for minimum number of occurrences.
If upper.Matches(pwd).Count < numUpper Then Return False
If lower.Matches(pwd).Count < numLower Then Return False
If number.Matches(pwd).Count < numNumbers Then Return False
If special.Matches(pwd).Count < numSpecial Then Return False
' Passed all checks.
Return True
End Function
Sub TestValidatePassword()
Dim password As String = "Password"
' Demonstrate that "Password" is not complex.
MsgBox(password & " is complex: " & ValidatePassword(password))
password = "Z9f%a>2kQ"
' Demonstrate that "Z9f%a>2kQ" is not complex.
MsgBox(password & " is complex: " & ValidatePassword(password))
End Sub