/// <summary>
 /// Add client and switching to an another window
 /// </summary>
 /// <param name="sender"></param>
 /// <param name="e"></param>
 private void NextButton_Click(object sender, RoutedEventArgs e)
 {
     try
     {
         // first checking if the client is eligibe to perfom order
         if (bl.isEligibedForOrder(client))
         {
             // calling function
             bl.AddClient(client);
             // reinitialize data
             client           = new Client();
             this.DataContext = client;
             // switching window
             Switcher.Switch(new NewOrderWindow());
         }
     }
     // catch excpetion
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message);
     }
 }