Is Palindrome

Imports System.Text.RegularExpressions

Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim s As String
        Dim IsItAPalindrome_1 As Boolean
        Dim IsItAPalindrome_2 As Boolean
        Dim IsItAPalindrome_3 As Boolean

        ' these function have been tested on the worlds longest Palindrome at
        ' http://norvig.com/pal17txt.html a Palindrome over 17000 words long

        ' OK lest get started... strip out all punctuation
        s = CleanInput(RichTextBox1.Text) ' you will need a RichTextBox1 to test the monster 17000 word Palindrome

        ' 3 functions
        IsItAPalindrome_1 = CheckPalindrome(s)
        IsItAPalindrome_2 = IsPalindrome(s)
        IsItAPalindrome_3 = IsPalindrome_new(s)

    End Sub
    Function CleanInput(strIn As String) As String
        ' strip out all punctuation... yep, my old favorite regular expressions again
        Return Regex.Replace(strIn.ToLower, "[^A-Za-z0-9]+", String.Empty)
    ' what we are doing there is stripping out everything except anything between the []
    End Function

    ' Credited to http://www.authorcode.com/how-to-check-whether-string-is-a-palindrome-or-not-using-vb-net/
    ' Function 1
    Private Function CheckPalindrome(ByVal strString As String) As Boolean
        Dim str As String
        str = StrReverse(strString)
        If str.Equals(strString) Then
            Return True
        Else
            Return False
        End If
    End Function

    ' Function 2
    Public Function IsPalindrome(s As String) As Boolean
        Dim i As Integer = 0
        Dim j As Integer = s.Length - 1
        While i < j
            If s(i) <> s(j) Then
                Return False
            End If
            i += 1
            j -= 1
        End While
        Return True
    End Function

    ' Function 3
    Public Function IsPalindrome_new(src As String) As Boolean
        Dim palindrome As Boolean = True
        For i As Integer = 0 To src.Length \ 2
            If src(i) <> src(src.Length - i - 1) Then
                palindrome = False
                Exit For
            End If
        Next
        Return palindrome
    End Function

End Class