private void button_Click(object sender, RoutedEventArgs e)
 {
     try
     {
         if (textBox.Text == "" || textBox_Copy.Text == "" || textBox_Copy1.Text == "" || textBox_Copy2.Text == "" || bankAccountText.Text == "" || textBox_Copy4.Text == "" || passwordBox.Password == "")
         {
             throw new ArgumentNullException("You need to fill all fields");
         }
         if (bankNameCombo.SelectedIndex == -1 || branchNameCombo.SelectedIndex == -1)
         {
             throw new ArgumentNullException("You need to fill all fields");
         }
         bl.AddHost(host);
         HostGrid.Children.RemoveAt(0);
         HostGrid.Children.Add(new HostHostingUnits(host, HostGrid));
         RulerGrid.Children.RemoveAt(0);
         RulerGrid.Children.Add(new HostRuler(host, HostGrid, RulerGrid));
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message);
     }
 }