The pager link makes a
GET
request. It does not pass across any other fields from your form.
To resolve this, you'll need to use Javascript to intercept the click event on the page links, and submit the form instead.
This StackOverflow answer[
^] describes how:
@Html.HiddenFor(x => x.Page, new { id = "page" })
$(function () {
$('tfoot a').click(function () {
var page = this.href.match(/page=([0-9])+/)[1];
$('#page').val(page);
$('form').submit();
return false;
});
});