how to encode the CSS text on web application pages

Question

Hi team

 

working on css attacks validation code c# and they injecting the script in this way

 

%uff1cscript%uff1ealert%uff08123456%uff09%uff1c/script%uff1e and from the server side how to encode this text

 

to find out the it contans html code or not i am using following way to encode but its not working 

 

System.Web.HttpUtility.HtmlDecode or  HttpContext.Current.Server.HtmlEncode 

 

let us know how to validate it

 

Thanks in advance