public class CssLink : HtmlLink
{
    public CssLink()
    {
    }

    protected override void Render(HtmlTextWriter writer)
    {
        UpdateFile();
        base.Render(writer);
    }

    protected void UpdateFile()
    {
        string absRealPath = this.Page.Server.MapPath(this.Href);
        string hrefResolvedPath = this.Href.Replace(".css", "_resolved.css");
        string absResolvedPath = this.Page.Server.MapPath(hrefResolvedPath);

        //Update the href property w
        this.Href = hrefResolvedPath;
        FileInfo fiReal = new FileInfo(absRealPath);
        FileInfo fiResolved = new FileInfo(absResolvedPath);

        if(!fiReal.Exists)
            return;

        //If the last modified date of the resolved css file is greater than the real css file
        //and the resolved file exists, skip update
        if(fiResolved.Exists && fiReal.LastWriteTime < fiResolved.LastWriteTime)
        {
            this.Page.Trace.Warn("CSS Update", "CSS file already up to date");
            return;
        }

        this.Page.Trace.Warn("CSS Update", "Begin update CSS file with resolved application path");
        if(fiResolved.Exists)
            fiResolved.Delete();

        string contents = null;
        using(FileStream fs = new FileStream(absRealPath, FileMode.Open, FileAccess.Read))
        {
            using(StreamReader sr = new StreamReader(fs))
            {
                contents = sr.ReadToEnd();
                sr.Close();
            }
            fs.Close();
        }

        using(StreamWriter sw = new StreamWriter(absResolvedPath, false))
        {
            string relAppPath = HttpRuntime.AppDomainAppVirtualPath;
            if(!relAppPath.EndsWith("/"))
                relAppPath += "/";

            sw.Write(contents.Replace("http://www.csharper.net/", relAppPath));
            sw.Close();
        }

        fiReal = null;
        fiResolved = null;
        this.Page.Trace.Warn("CSS Update", "End update");
    }
}