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private void button4_Click(object sender, RoutedEventArgs e)
        {
            StreamReader datei = new StreamReader(Pfad);
            string[] lines = { datei.ToString() };
            datei.Close();
            System.IO.File.WriteAllLines(Pfad, lines);

            using (System.IO.StreamWriter file = new System.IO.StreamWriter(Pfad))
            {
                foreach (string line in lines)
                {
                    if (line.Contains("Test") == false)
                    {
                        file.WriteLine(line);
                    }
                }
            }
 
        }