问C#中的条件正则问题

EN

<ahref="samplesample?=ASAsq96\%#');"</a>

http://www.test.com/ASA[a-z][a-z][0-9][0-9]/example

http://www.stack.com/ASA[a-z][a-z][0-9][0-9]

 http://replaceme/ASA[a-z][a-z][0-9][0-9] 

mail.HTMLBody = Regex.Replace(mail.HTMLBody, 
"(?<!http://([\\w+?\\.\\w+])+([a-zA-Z0-9\\~\\!\\@\\#\\$\\%\\^\\&amp;
\\*\\(\\)_\\-\\=\\+\\\\\\/\\?\\.\\:\\;\\'\\,]*)?)
(ASA[a-z][a-z][0-9][0-9])(?!</a>)", 
"<a href=\"http://www.stack.com?order=$&\">$&</a>");