Función IsAlphabetic Ejercicio VB.Net - Curso de Programación Visual Basic

Imports System
Public Class exercise123
    Public Shared Function IsAlpha(ByVal simbolo As Char) As Boolean
        If (simbolo >= "a"c) AndAlso (simbolo <= "z"c) Then Return True
        If (simbolo >= "A"c) AndAlso (simbolo <= "Z"c) Then Return True
        Return False
    End Function

    Public Shared Function IsAlpha2(ByVal simbolo As Char) As Boolean
        simbolo = Char.ToLower(simbolo)
        If (simbolo >= "a"c) AndAlso (simbolo <= "z"c) Then Return True
        Return False
    End Function

    Public Shared Function IsAlpha3(ByVal simbolo As Char) As Boolean
        simbolo = simbolo.ToString().ToLower()(0)
        If (simbolo >= "a"c) AndAlso (simbolo <= "z"c) Then Return True
        Return False
    End Function

    Public Shared Function IsAlpha4(ByVal simbolo As Char) As Boolean
        Dim validas As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqwrstuvwxyz"
        If validas.Contains(simbolo) Then Return True
        Return False
    End Function

    Public Shared Sub Main()
        Console.WriteLine(IsAlpha("w"c))
        Console.WriteLine(IsAlpha("2"c))
    End Sub
End Class