VB - TextBox mit Eingabefilter

Option Strict On
Option Explicit On
Option Infer Off

Imports System.ComponentModel

Public Class TextBoxExtended : Inherits TextBox

    Private _FilterType As FilterType = FilterType.Forbidden
    <Category("Filter")>
    Public Property FilterType() As FilterType
        Get
            Return _FilterType
        End Get
        Set(ByVal value As FilterType)
            _FilterType = value
            Invalidate()
        End Set
    End Property

    Public _Filter As String = String.Empty
    <Category("Filter")>
    Public Property Filter() As String
        Get
            Return _Filter
        End Get
        Set(ByVal value As String)
            _Filter = value
            Invalidate()
        End Set
    End Property

    Private Sub Me_TextChanged(sender As Object, e As EventArgs) Handles Me.TextChanged
        Dim caretPosition As Integer = SelectionStart
        Select Case FilterType
            Case FilterType.Allowed
                For Each _char As Char In Text.ToCharArray
                    If Not Filter.Contains(_char) Then
                        Text = Text.Replace(_char, String.Empty)
                    End If
                Next
            Case FilterType.Forbidden
                For Each _char As Char In Filter.ToCharArray
                    Text = Text.Replace(_char, String.Empty)
                Next
        End Select
        SelectionStart = caretPosition
    End Sub

End Class

Public Enum FilterType
    Allowed
    Forbidden
End Enum