[VB.NET] รบกวนสอบถามเกี่ยวกับการสร้าง Function ที่กำหนด parameter ต้องเป็นค่านี้เท่านั้น

Public Enum Number As Integer
        One = 1
        Two = 2
        Three = 3
        Four = 4
    End Enum

Public Function MyFunction(ByVal TEST As String, Optional ByVal Value As Number = Number.One)
        Return TEST
End Function

Imports System.ComponentModel
Public Class paramCodeDesigetimeValidator
    Implements INotifyPropertyChanged
    Private _FuckMe As String = String.Empty
    Public Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged

    Private Sub NotifyPropertyChanged(ByVal info As String)
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info))
    End Sub
    Sub New()
        _FuckMe= "No Hair"
    End Sub
    Public Property FuckMe() As String
        Get
            Return Me._FuckMe
        End Get
        Set(value As String)
            If value <> Me._FuckMeThen
                Me._FuckMe= value
                NotifyPropertyChanged("Fuck me change.")
            End If
        End Set
    End Property
End Class