private void voegToeButton_Click(object sender, RoutedEventArgs e)
 {
     string directory = MaakPad();
     try
     {
         Check();
         if (IsMailGebruikt())
         {
             MessageBox.Show("email is used!!!");
         }
         else
         {
             System.IO.Directory.CreateDirectory(directory);
             System.IO.Directory.CreateDirectory(System.IO.Path.Combine(directory, "Kennis"));
             System.IO.Directory.CreateDirectory(System.IO.Path.Combine(directory, "Taal"));
             System.IO.Directory.CreateDirectory(System.IO.Path.Combine(directory, "Wiskunde"));
             SchrijfTxt(directory);
             Login back = new Login();
             back.Left = 400;
             back.Top = 200;
             back.Show();
             this.Hide();
         }
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message);
     }
 }
 private void terugButton_Click(object sender, RoutedEventArgs e)
 {
     Login l = new Login();
     l.Left = 400;
     l.Top = 200;
     l.Show();
     this.Close();
 }