Change CSS classes from code

I’ve taken AnthonyWJones original code and amended it so that it works no matter what scenario:

static class WebControlsExtensions
    {
        public static void AddCssClass(this WebControl control, string cssClass)
        {
            List<string> classes = control.CssClass.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();

            classes.Add(cssClass);

            control.CssClass = classes.ToDelimitedString(" ");
        }

        public static void RemoveCssClass(this WebControl control, string cssClass)
        {
            List<string> classes = control.CssClass.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToList();

            classes.Remove(cssClass);

            control.CssClass = classes.ToDelimitedString(" ");
        }
    }

    static class StringExtensions
    {
        public static string ToDelimitedString(this IEnumerable<string> list, string delimiter)
        {
            StringBuilder sb = new StringBuilder();
            foreach (string item in list)
            {
                if (sb.Length > 0)
                    sb.Append(delimiter);

                sb.Append(item);
            }

            return sb.ToString();
        }
    }