Asp.net: pass client information

I'm building a website with asp.net mvc and there is some data that I need to consult with every browser request. This contains the clients date and its latitude/longitude. This way we can update the users (using a PDA) location.

If we assume that I already have the latitude & longitude, how can I pass it to 开发者_如何学Gothe webserver with every browser request?

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HTTP headers (and cookies in particular) look like an appropriate place.