Custom HtmlHelper with Html5 time and date support

htmlhelper.cs

        public static IHtmlString SkinnedTextBoxFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, InputStyles styles = InputStyles.Normal, int size = 0)
        {
            var cssClasses = BuildClasses(styles, "input");
            IDictionary<string, object> attrs = new Dictionary<string, object>();
            attrs["class"] = cssClasses;
            if (size > 0)
                attrs["size"] = size;

            string format = null;
            if (typeof (DateTime).IsAssignableFrom(expression.ReturnType))
            {
                attrs["type"] = "date";
                format = "{0:yyyy-MM-dd}";
            }
            else if (typeof (TimeSpan).IsAssignableFrom(expression.ReturnType))
            {
                attrs["type"] = "time";
                format = "{0:hh':'mm}";
            }

            return html.TextBoxFor(expression, format, attrs);
        }