Coronavirus project at work - April 30, 2020 - make it simple, more readable

CSharpShowcase.cs

  /// <summary>
        /// code review on April 24, 2020 
        /// add id in html for each div element to make code readable
        /// 
        /// Code review on July 7, 2017
        /// March 14, 2016
        /// Cannot be extracted, because Server.MapPath(pngFile) <- check IIS server file exists or not 
        /// January 4, 2016
        /// Add "ABS" to the list
        /// </summary>
        /// <param name="mainMenu"></param>
        /// <param name="subMenu"></param>
        /// <param name="name"></param>
        /// <param name="imagePath"></param>
        /// <param name="text"></param>
        /// <param name="products"></param>
        /// <returns></returns>
        public static string prepareHtml(
            string mainMenu,
            string subMenu,
            string name,
            string imagePath,
            string text,
            IEnumerable<PictureSlideColumns> products)
        {
            string urlKey = getUrlStr(mainMenu, subMenu);

            string imgUrlHelper = Image_render.getHelperString(name, urlKey, imagePath);

            string cssClass = CssClassTitle.GetName(text);

            string html = "";           

            for (int i = 0; i < products.Count(); i++)
            {
                var visit = products.ElementAt(i);
                var mountName    = visit.MountName;
                var mountWebName = visit.MountOnWeb;
                var subTitle     = visit.SubTitle;

                var fileName = imgUrlHelper + mountName;

                // HOLD: if .png img file exists, then .png will be displayed; otherwise, go for .img file 
                string imageFile = fileName + ".jpg";               
               
                var index = i.ToString();
                var prefixs = new string[] {"titleDiv" + index,"subTitleDiv" + index,"imgDiv" + index};

                var list = new List<string>();               

                list.Add(composeOuterDiv(cssClass, prefixs[0], mountWebName));
                list.Add(MainSlideShow.Html.HtmlDivSubTitle.Compose(prefixs[1], subTitle));               
                list.Add(getImageHtml(prefixs[2], imageFile));               

                // a div for each product
                var htmlDiv = "";
                var finishClass = getFinishClass(name, mountName); 

                htmlDiv += "<div class=\"slide " + finishClass + "\">";
                htmlDiv += String.Join("", list.ToArray());                
                htmlDiv += "</div>";

                html += htmlDiv;
            }

            return html;
        }

        /// <summary>
        /// April 27, 2020
        /// add div id for each div
        /// </summary>
        /// <param name="cssClass"></param>
        /// <param name="divName"></param>
        /// <param name="mountWebName"></param>
        /// <returns></returns>
        private static string composeOuterDiv(string cssClass, string divName, string mountWebName)
        {
            return "<div id=\"" + divName + "\" class=\"mount_id " + cssClass + "\" class=\"grid_2\">" + mountWebName + "</div>"; 
        }