Simple indexed prefix for razor foreach loop

Example.cshtml

@foreach (var item in Html.Prefix(Model.Results, "result")) {
    <label for="@Html.Id("comment")>Comment</label>
    @Html.TextArea("comment", item.Comment)
}

@using (Html.Prefix("test")) {
    <label for="@Html.Id("nested")">Nested</label>
    @Html.TextArea("nested")
}

<label for="@Html.Id("notes")>Notes</label>
@Html.TextArea("notes", Model.Notes)


@* Output:

<label for="result_0__comment">Comment</label>
<textarea id="result_0__comment" name="result[0].comment"></textarea>

<label for="result_1__comment">Comment</label>
<textarea id="result_1__comment" name="result[1].comment"></textarea>

<label for="result_2__comment">Comment</label>
<textarea id="result_2__comment" name="result[2].comment"></textarea>

<label for="test_nested">Nested</label>
<textarea id="test_nested" name="test.nested"></textarea>

<label for="notes">Notes</label>
<textarea id="notes" name="notes"></textarea>
*@

PrefixExtentions.cs

using System;
using System.Collections.Generic;
using System.Web.Mvc;

public static class PrefixExtensions
{
    public static HtmlNamePrefixRegion Prefix (this HtmlHelper html, string prefix)
	{
		var templateInfo = html.ViewData.TemplateInfo;
		var fullPrefix = templateInfo.GetFullHtmlFieldName (prefix);
		return new HtmlNamePrefixRegion (templateInfo, fullPrefix);
	}

	public static HtmlIndexedNamePrefixRegion Prefix (this HtmlHelper html, string prefix, int index)
	{
		var templateInfo = html.ViewData.TemplateInfo;
		return new HtmlIndexedNamePrefixRegion (templateInfo, prefix, index);
	}

	public static IEnumerable<T> Prefix<T> (this HtmlHelper html, IEnumerable<T> items, string prefix)
	{
		return html.Prefix (items, prefix, 0);
	}

	public static IEnumerable<T> Prefix<T> (this HtmlHelper html, IEnumerable<T> items, string prefix, int initialIndex)
	{
		using (var counter = html.Prefix (prefix, initialIndex)) {
			foreach (var item in items) {
				yield return item;
				counter.Next ();
			}
		}
	}
}

public class HtmlIndexedNamePrefixRegion : IDisposable
{
	private readonly TemplateInfo template;
	private readonly string originalPrefix;
	private readonly string partialPrefix;
	private int index;

	public HtmlIndexedNamePrefixRegion (TemplateInfo template, string partialPrefix, int initialIndex)
	{
		this.template = template;
		this.partialPrefix = partialPrefix;
		index = initialIndex;
		originalPrefix = template.HtmlFieldPrefix;
		Update ();
	}

	public void Next ()
	{
		index++;
		Update ();
	}

	private void Update ()
	{
		template.HtmlFieldPrefix = originalPrefix;
		var fullPrefix = template.GetFullHtmlFieldName (string.Format ("{0}[{1}]", partialPrefix, index));
		template.HtmlFieldPrefix = fullPrefix;
	}

	public void Dispose ()
	{
		template.HtmlFieldPrefix = originalPrefix;
	}
}

public struct HtmlNamePrefixRegion : IDisposable
{
	private readonly TemplateInfo template;
	private readonly string originalPrefix;

	public HtmlNamePrefixRegion (TemplateInfo template, string newPrefix)
	{
		this.template = template;
		originalPrefix = template.HtmlFieldPrefix;
		template.HtmlFieldPrefix = newPrefix;
	}

	public void Dispose ()
	{
		template.HtmlFieldPrefix = originalPrefix;
	}
}