public static void ReplaceRule(File input, string oldRuleName, StylesheetRule rule)
{
var contents = Encoding.UTF8.GetString(input.ContentBytes);
var ruleRegex = new Regex(string.Format(_ruleRegexFormat, oldRuleName), RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.Singleline);
contents = ruleRegex.Replace(contents, rule != null ? rule.ToString() : "");
input.ContentBytes = Encoding.UTF8.GetBytes(contents);
}