/// <summary>
        /// Constructor for Main Window
        /// </summary>
        public MainWindow()
        {
            try
            {
                InitializeComponent();
                Application.Current.ShutdownMode = ShutdownMode.OnMainWindowClose;

                ml = new clsMainLogic();
                //Populate Items ComboBox
                cmbInvoiceItem.ItemsSource = ml.getItems().Select(a => a.ItemDesc);

                //Populate DataGrid with Invoices
                List <clsInvoice> invoice = ml.GetAllInvoices();
                dgInvoices.ItemsSource = invoice;
            }
            catch (Exception ex)
            {
                HandleError(MethodInfo.GetCurrentMethod().DeclaringType.Name,
                            MethodInfo.GetCurrentMethod().Name, ex.Message);
            }
        }
        /// <summary>
        /// Click on this button and it will navigate you to the Edit Items Window
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void itemItems_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                itemsWindow = new wndItems();

                this.Hide();

                itemsWindow.ShowDialog();

                //Update all dropdowns to reflect any changes (dropdown.itemsSource =)

                this.Show();

                cmbInvoiceItem.ClearValue(ItemsControl.ItemsSourceProperty);
                cmbInvoiceItem.ItemsSource = ml.getItems().Select(a => a.ItemDesc);
            }
            catch (Exception ex)
            {
                HandleError(MethodInfo.GetCurrentMethod().DeclaringType.Name,
                            MethodInfo.GetCurrentMethod().Name, ex.Message);
            }
        }