Templated Partials

HtmlHelperExtensions.cs

    public static MvcHtmlString TemplatedPartial(this HtmlHelper helper, string partialName, object model, string[] names, params Func<object, HelperResult>[] templates)
    {
      if (names.Length < templates.Length)
        throw new InvalidOperationException("Please provide a name for each template.");

      var viewData = new ViewDataDictionary(helper.ViewData);

      var templateResults = new Dictionary<string, HelperResult>();

      viewData["::PartialTemplates::"] = templateResults;

      for (var i = 0; i < templates.Length; i++)
      {
        templateResults[names[i]] = templates[i](null);
      }

      return helper.Partial(partialName, model, viewData);
    }

    public static HelperResult Template(this HtmlHelper helper, string templateName)
    {
      var templateResults = helper.ViewData["::PartialTemplates::"] as Dictionary<string, HelperResult>;

      if (templateResults == null)
        throw new InvalidOperationException("No templates exist in the current context.");

      return templateResults.ContainsKey(templateName) ? templateResults[templateName] : new HelperResult(t => { });
    }

    public static bool TemplateExists(this HtmlHelper helper, string templateName)
    {
      var templateResults = helper.ViewData["::PartialTemplates::"] as Dictionary<string, HelperResult>;

      if (templateResults == null)
        return false;

      return templateResults.ContainsKey(templateName);
    }

Main.cshtml

@{ var test = "Yipee"; }

@Html.TemplatedPartial("Section", new []{"header", "toolbar", "content"},
  @<b>Header</b>,
  @<i>toolbar</i>,
  @<text>this is the content of the box. <div>@test</div></text>)

Section.cshtml

<div class="section">
  <div class="section-heading-container">
    <div class="section-heading">
      @Html.Template("header")

      @if( Html.TemplateExists("toolbar") )
      {
        <div class="toolbar">
          @Html.Template("toolbar")
        </div>
      }
    </div>
  </div>
  <div class="section-content-container">
    <div class="section-content">
      @Html.Template("content")
    </div>
  </div>
</div>