private void invoiceIDComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            ///Disable other drop down menu's if this is selected
            if (invoiceIDComboBox.IsEnabled)
            {
                invoiceDateComboBox.IsEnabled   = false;
                invoiceAmountComboBox.IsEnabled = false;
            }

            ///The two other drop down menu's will be disbled when this is being used

            ///When selected this combo box will show a drop down list with invoice ID's
            ///The user will be able to highlight/select an ID and it will be recieved
            ///by the dataGrid1 to show that specific invoice only
            Console.Write("textbox Value: " + invoiceIDComboBox.SelectedItem);

            //get query needed find invoice
            String sQuery = mydb.SelectInvoiceID(invoiceIDComboBox.SelectedItem.ToString());

            //datatable used to fget table data.
            dt = db.FillSqlDataTable(sQuery);

            //fill the datagrid
            invoiceGrid1.ItemsSource = dt.DefaultView;
        }