Upload de imagem TinyMCE

Upload.cs

        public string Upload(HttpPostedFileBase file)
        {
            string path;
            string saveloc = "~/Uploads/Imagens";
            string relativeloc = "/Uploads/Imagens/";
            string filename = file.FileName;

            if (file != null && file.ContentLength > 0 && IsImage(file))
            {
                try
                {
                    path = Path.Combine(HttpContext.Server.MapPath(saveloc), Path.GetFileName(filename));
                    file.SaveAs(path);
                }
                catch (Exception e)
                {
                    return "<script>alert('Failed: " + e + "');</script>";
                }
            }
            else
            {
                return "<script>alert('Failed: Unkown Error. This form only accepts valid images.');</script>";
            }

            return "<script>top.$('.mce-btn.mce-open').parent().find('.mce-textbox').val('" + relativeloc + filename + "').closest('.mce-window').find('.mce-primary').click();</script>";
        }