Option Explicit On
 
' ### Die benötigten Bibliotheken 
Imports System.Windows.Forms
Imports System.Collections
Imports System
Imports System.Drawing
 
' ### Der Namespace 
Namespace AutoTextbox
 
    Public Class TextBox_Datum
        Inherits TextBox
 
        Public Event ValidateTextEnter()
 
        Private Function Validate(ByVal txt As String) As Boolean
            Dim datum As Date
            If DateTime.TryParseExact(Me.Text.Trim, "dd.MM.yyyy", New  _
              Globalization.CultureInfo("de-DE"), _
              Globalization.DateTimeStyles.None, datum) Then
                Return True
            Else
                Return False
            End If
        End Function
 
        Private Sub TextBox_Datum_Leave(ByVal sender As Object, ByVal e As _
          System.EventArgs) Handles Me.Leave
            If Validate(Me.Text) Then
                RaiseEvent ValidateTextEnter()
            Else
                MsgBox("Falsche Eingabe", MsgBoxStyle.Information)
                Me.Focus()
            End If
        End Sub
 
    End Class
 
End Namespace

 Private Sub Textbox_Datum Handles Textbox_Datum.ValidateTextEnter
       '### hier kann weiter Code stehen in meinem Fall wird der der Inhalt der 
       ' Textbox gespeichert
        speichern()
    End Sub