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?

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

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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