Reading header.php/footer.php to a text string

I am attempting to read the results of the executed header.php/footer.php files as a string of html. Here’s the scenario:

There are pages in the site that are developed in a .net environment but they want to share common headers/footers across the entire domain. They wish to have WordPress be the repository for this code and any time there is an update have a PHP cURL call to a .net web service and feed it the new HTML for the header/footers.

I tried calling get_header() but that does not return a string (as I anticipated) so then I tried this test solution in functions.php:

function write_header() {
	$header_content = file_get_contents(get_bloginfo('wpurl').'/index.php' );
	$fp = fopen('c:\header.txt', 'a+');
	fwrite($fp, $header_content);//just testing the output, this will be a cURL call eventually.
	fclose($fp);
}
add_action( 'wp_update_nav_menu', 'write_header' );

It seems to be a very heavy handed method of getting the HTML since I’ll have to do a lot of string manipulation to parse out the pieces I want. Is there a simpler way of doing this that I’m missing?