The Shipping user control (Shipping.ascx) only validates the shipping address zip code, even though some methods may also require City and Region. I have attached a modified version of Shipping.ascx.vb that scans the applicable shipping methods and then checks the associated provider to see if City, Region, and/or PostalCode is required. If it is and the corresponding field is blank then the appropriate message is displayed.


I also added some code so that a small script is injected into the page. You can call the script from the Checkout page (Checkout.aspx) to display a short message while retrieving rates. For example,