only specific city related products show to the customer when customer select specific city

How / where does "customer select specific city"?

New York wrote:.

I think city drop-down should be in header so this selection is more convenient.

I think city drop-down should be in header so this selection is more convenient.
You think right sir I am creating the city drop-down for selecting the specific city in header but my problem is only where to apply the query to products from where to fetch.
Only my problem is I can't find this query from where to products are fetch, so please give me the successful suggestion for solve my problem

Hi,
Were you able to do this? If yes, can you please guide how it can be done.