ASP.Net calculate City from ZIP?

i have a user registration. In this, of course, a user must enter ZIP.

Now I will make a way in which the city is be calculate from the ZIP.

The only idea I have by myself is a database-table (or txt-file) and look in the table / file for the city.

Is this the best / fastest way or is there anoth开发者_JS百科er?

Hosting the database yourself is one possibility, another is to use some service on the cloud. Here's one such service.

If you have your own database, you will have the job of keeping it upto date.

Better to use an internet service. Try this one: http://www.webservicex.net/uszip.asmx