Recursion in an ASP.NET MVC view

Create your own HtmlHelper extension method like so:

namespace System.Web.Mvc
{
    public static class HtmlHelperExtensions
    {
        public static string CategoryTree(this HtmlHelper html, IEnumerable<Category> categories)
        {
            string htmlOutput = string.Empty;

            if (categories.Count() > 0)
            {
                htmlOutput += "<ul>";
                foreach (Category category in Categories)
                {
                    htmlOutput += "<li>";
                    htmlOutput += category.Name;
                    htmlOutput += html.CategoryTree(category.Categories);
                    htmlOutput += "</li>";
                }
                htmlOutput += "</ul>";
            }

            return htmlOutput;
        }
    }
}

Funny you should ask because I actually created one of these just yesterday.