Helper to reduce the amount of Bootstrap 3.0 chrome that needs to be manual written around standard HtmlHelper extensions

BootstrapHelper

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.WebPages;
using System.Linq.Expressions;
using System.Web.Mvc.Html;
using System.Text;

namespace System.Web.Mvc
{
    public static class BootstrapHelper
    {
        public static IDisposable BeginFields(this HtmlHelper helper)
        {
            helper.ViewContext.Writer.Write(helper.AntiForgeryToken());
            helper.ViewContext.Writer.Write("<div class=\"form-horizontal\">");

            return new EndFields(helper);
        }

        class EndFields : IDisposable
        {
            private HtmlHelper helper;

            public EndFields(HtmlHelper helper)
            {
                this.helper = helper;
            }

            public void Dispose()
            {
                this.helper.ViewContext.Writer.Write("</div>");
            }
        }

        public static MvcHtmlString Field<T, V>(this HtmlHelper<T> helper, Expression<Func<T, V>> member, Func<Expression<Func<T, V>>, HelperResult> template)
        {
            return Concat(
                StartHtml("div", b => b.AddCssClass("form-group")),
                helper.LabelFor(member, new { @class = "control-label col-md-2" }),
                StartHtml("div", b => b.AddCssClass("col-md-10")),
                MvcHtmlString.Create(template(member).ToHtmlString()),
                EndHtml("div"),
                EndHtml("div")
                );
        }

        public static MvcHtmlString SubmitButton(this HtmlHelper helper, string value)
        {
            return Concat(
                StartHtml("div", b => b.AddCssClass("form-group")),
                StartHtml("div", b => b.AddCssClass("col-md-offset-2 col-md-10")),
                BuildHtml("input", b => { b.AddCssClass("btn btn-default"); b.Attributes["type"] = "submit" ; b.Attributes["value"] = value; }),
                EndHtml("div"),
                EndHtml("div")
                );
        }

        private static MvcHtmlString StartHtml(string element, Action<TagBuilder> builder)
        {
            return BuildHtml(element, builder, TagRenderMode.StartTag);
        }

        private static MvcHtmlString EndHtml(string element)
        {
            return BuildHtml(element, null, TagRenderMode.EndTag);
        }

        private static MvcHtmlString BuildHtml(string element, Action<TagBuilder> buildUp, TagRenderMode mode = TagRenderMode.Normal)
        {
            TagBuilder tagBuilder = new TagBuilder(element);
            if (buildUp != null) buildUp(tagBuilder);
            return MvcHtmlString.Create(tagBuilder.ToString(mode));
        }

        private static MvcHtmlString Concat(params MvcHtmlString[] items)
        {
            var sb = new StringBuilder();
            foreach (var item in items.Where(i => i != null))
                sb.Append(item.ToHtmlString());
            return MvcHtmlString.Create(sb.ToString());
        }
    }
}