private async void btnAdd_Click(object sender, EventArgs e)
{
Product product = new Product()
{
ProductName = txtProductName.Text,
CategoryId = (int)cmbCategories.SelectedValue,
UnitPrice = decimal.Parse(txtUnitPrice.Text),
UnitsInStock = short.Parse(txtUnitsInStock.Text)
};
bool result = await _productPrecessor.AddProduct(product);
await GetList();
}