Hi, Thanks for your response. It really is helpful. By the way, I forgot another thing. Is there a way to replace <MyTag MyTagId="123"> with my custom HTML once I extracted the MyTagId value (123 in this case).   Thanks. 

I am developing asp.net c# web application and I want an expression that will get only numerical value of a custom tag. Example tag: <MyTag MyTagId="123">  I need an expression that will extract 123 from MyTagId attribute of MyTag. Your help will be highly appreciated.   Thanks.