private void BtnRegistration_Click_1(object sender, RoutedEventArgs e)
 {
     MainWindow loginWindow = new MainWindow();
     loginWindow.Show();
     this.Close();
 }
 private void BtnBack_Click(object sender, RoutedEventArgs e)
 {
     MainWindow loginWindow = new MainWindow();
     loginWindow.Show();
     this.Close();
 }