WordPress at a glance
function is not described

iis7_rewrite_rule_exists() WP 2.8.0

Check if rewrite rule for WordPress already exists in the IIS 7+ configuration file

No Hooks.

Return

true/false.

Usage

iis7_rewrite_rule_exists( $filename );
$filename(string) (required)
The file path to the configuration file

Code of iis7 rewrite rule exists: wp-admin/includes/misc.php VER 5.0.3

<?php
function iis7_rewrite_rule_exists($filename) {
	if ( ! file_exists($filename) )
		return false;
	if ( ! class_exists( 'DOMDocument', false ) ) {
		return false;
	}

	$doc = new DOMDocument();
	if ( $doc->load($filename) === false )
		return false;
	$xpath = new DOMXPath($doc);
	$rules = $xpath->query('/configuration/system.webServer/rewrite/rules/rule[starts-with(@name,\'wordpress\')] | /configuration/system.webServer/rewrite/rules/rule[starts-with(@name,\'WordPress\')]');
	if ( $rules->length == 0 )
		return false;
	else
		return true;
}