private void btnEdit_Click(object sender, RoutedEventArgs e)
        {
            Storyboard sb;
            if (_isExpanded != true)
            {
                sb = this.FindResource("gridin") as Storyboard;
                sb.Begin(this);
                _isExpanded = !_isExpanded;
            }

            var selectedCustomer = dcCustomersList.SelectedItem as CustomersView;

            if (selectedCustomer != null)
            {
                CustomersForm.CustomerId = selectedCustomer.CustomerID;

                var page = new CustomersForm();
                navigation.Navigate(page);
            }
            else
            {
                NullMessage();
            }
        }
        private void btnAdd_Click(object sender, RoutedEventArgs e)
        {
            CustomersForm.CustomerId = 0;
              
            Storyboard sb;
            if (_isExpanded != true)
            {
                sb = this.FindResource("gridin") as Storyboard;
                sb.Begin(this);
                _isExpanded = !_isExpanded;
            }

            var page = new CustomersForm();
            navigation.Navigate(page);
        }