Writing SEO friendly url gets infinite loop asp net

Question

I am trying to write SEO friendly URL for my website. i am using  global.asax. 

protected void Ap

But When the regular expression matches, the code goes on infinite loop. When I apply debugger in this code, It moves infinitely when the regular expression Matches.

This is the code that I have used 

protected void Application_BeginRequest(object sender, EventArgs e)
    {

        HttpContext incoming = HttpContext.Current;
        string oldpath = incoming.Request.Path;
        string imgId = string.Empty;
        //   string imgName = string.Empty;
        Regex regex = new Regex(@"N/(.+)", RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace);
        MatchCollection matches = regex.Matches(oldpath);

        if (matches.Count > 0)
        {

            imgId = matches[0].Groups[1].ToString();
            // imgName = matches[0].Groups[2].ToString();
            string newPath = String.Concat("~/inner.aspx?Id=", imgId);
            incoming.RewritePath(String.Concat("~/inner.aspx?Id=", imgId), false);
        }

    }

Answer 1

you should know that regex avoid cases  thus n is caught before the first /.

You need either to get the last n and everything that is not /:

Regex regex = new Regex(@"N/([^/]+)$", RegexOptions.IgnoreCase);
Or, use a case sensitive search:

Regex regex = new Regex(@"N/(.+)");