using System.Text.RegularExpressions;

​

using System;

​

public class Program

{

    public static void Main()

    {

        var value=@"<script>alert();<ScriPT/>";

        Console.WriteLine(Regex.Replace(value, 

        @"</?(?i:script|embed|object|frameset|frame|iframe|meta|link|style)(.|\n|\s)*?>", 

        string.Empty, 

        RegexOptions.Singleline | RegexOptions.IgnoreCase));

    }

}