You have to use Javascript on the client side to get the lat and long using the Google Maps API V3.0
As far as I know, the api call uses ajax or something to fetch the data,
the object is below, and the lat and long is in the geometry location
var vA = $('[id*="_txt_JQuery_Google_Address_Destination"]').val();
var geocoder = new google.maps.Geocoder();
geocoder.geocode({ 'address': vA }, function (results, status) {
if (status != google.maps.GeocoderStatus.OK) {
alert("Initial geocode request was not successful for the following reason: " + status);
}
else {
results[0].geometry.location
}
});
[edit]
You may have to look for another source for geocoding, one that supports just a regular call to a web service, using asp.net.
You would have to reverse engineer the google map object, to fetch to parameters for it.
If you need just one set of geocode, then you call fetch the geocode in page load and opulate a hidden textbox, and then use asp.net to get the values.
[edit 2]
Now that I think about it, you could use .onclientClick = "fetch_GeoCode(address); return false;"
and run the Google Maps API to just get the geocode, and populate the hidden textboxes, you don't have have to draw a map technically.
There seems to be a ton of stuff out there for it, it would be location.lat and location.long
https://www.google.com/search?q=acess+google+geocode+from+asp.net&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a[
^]