Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) _
   Handles Button1.Click
 
        Dim file_open As New OpenFileDialog
        file_open.Filter = "csv-dateien|*.csv"
        file_open.AddExtension = True
 
 
        If file_open.ShowDialog = Windows.Forms.DialogResult.OK Then
            Dim auswahlListe As New List(Of String)
            For Each zeile As String In IO.File.ReadAllLines(file_open.FileName)
                If zeile.Contains("in stock") Then
                    auswahlListe.Add(zeile)
                End If
            Next
            RichTextBox1.Text = (String.Join(vbNewLine, auswahlListe.ToArray))
 
      End If
    End Sub