Identify axd file content type?

I've successfully created a module to minify asp.net default axd files that render only javascripts, but with AjaxControlToolkit I need to differentiate the content type weather it is css or image or javascript, please not that (Request/Response).ContentType is returning text/html

public class ParseAXD : IHttpModule
{
    public void Init(HttpApplication context)
    {
        context.BeginRequest += context_BeginRequest;
    }

    void context_BeginRequest(object sender, EventArgs e)
    {
        var context = HttpContext.Current;
        var path = context.Request.Url.PathAndQuery;
        if (path.ToLower().Contains(".axd") && IfNotWebClientRequest())
        {
            var remote = new Uri(Lib.SiteDb.DomainName + path);
            using (WebClient client = new WebClient())
            {
                string content = client.DownloadString(remote);

                //Need to identify the ContentType here, please not that (Request/Response).ContentType is returning text/html

                var settings = new CodeSettings();
                settings.MinifyCode = true;
                settings.LocalRenaming = LocalRenaming.CrunchAll;
                settings.RemoveFunctionExpressionNames = true;
                settings.EvalTreatment = EvalTreatment.MakeAllSafe;
                content = new Minifier().MinifyJavaScript(content, settings);
                context.Response.ContentType = "text/javascript";
                context.Response.Write(content);

                context.Response.Cache.SetValidUntilExpires(true);
                context.Response.Cache.SetExpires(DateTime.Now.AddMonths(1));
                context.Response.Cache.SetCacheability(HttpCacheability.Public);
                context.Response.Cache.SetOmitVaryStar(true);

                context.Response.Flush();
                context.Response.End();
            }
        }
    }