private void btnAdd_Click(object sender, EventArgs e)
        {
            // Opens AddProductType form and ensures no record is currently selected
            GlobalVariables.selectedProductTypeID = 0;
            frmAddProductType editForm = new frmAddProductType();

            editForm.ShowDialog();
            lvProductTypes.Items.Clear();
            DisplayProductTypes();
        }
        private void btnUpdate_Click(object sender, EventArgs e)
        {
            // Checks user has selected a product type
            if (lvProductTypes.SelectedItems.Count == 0)
            {
                MessageBox.Show("Please select a Product Type to update");
                return;
            }
            // Stores ProductID to be updated
            GlobalVariables.selectedProductTypeID = int.Parse(lvProductTypes.SelectedItems[0].Text);

            // Opens AddProductType form
            frmAddProductType editForm = new frmAddProductType();

            editForm.ShowDialog();
            lvProductTypes.Items.Clear();
            DisplayProductTypes();
        }