EditorTemplate for DropDownList

Option 1

Create an EditorTemplate named BootstrapSelect.cshtml

@model object
<div class="form-group">
  @Html.LabelFor(m => m, new { @class = "col-md-3 control-label" })
  <div class="col-md-9">
    @Html.DropDownListFor(m => m, (SelectList)ViewBag.Items, new { @class = "form-control"})
    @Html.ValidationMessageFor(m => m, null, new { @class = "help-block" })      
  </div>
</div>

and in the view

@Html.EditorFor(m => m.CategoryId, "BootstrapSelect")

but this means you would alway need to assign `ViewBag.Items in the controller

var categories = // get collection from somewhere
ViewBag.Items = new SelectList(categories, "ID", "CategoryName");

Option 2

Modify the EditorTemplate to accept additional ViewData

@model object
<div class="form-group">
  @Html.LabelFor(m => m, new { @class = "col-md-3 control-label" })
  <div class="col-md-9">
    @Html.DropDownListFor(m => m, (SelectList)ViewData["selectList"], new { @class = "form-control"})
    @Html.ValidationMessageFor(m => m, null, new { @class = "help-block" })      
  </div>
</div>

and in the view pass the SelectList in the additionalViewData parameter

@Html.EditorFor(m => m.CategoryId, "BootstrapSelect", new { selectList = new SelectList(ViewBag.Categories, "ID", "CategoryName") })

this is better in that you don’t need to rely on ViewBag. For example, if you had a view model with a property public SelectList CategoryItems { get; set; } then you could use

@Html.EditorFor(m => m.CategoryId, "BootstrapSelect", Model.CategoryItems)

Option 3

Create your own helper utilizing the built-in helper methods

using System;
using System.Linq.Expressions;
using System.Text;
using System.Web.Mvc;
using System.Web.Mvc.Html;

namespace YourAssembly.Html
{
  public static class BootstrapHelper
  {
    public static MvcHtmlString BootstrapDropDownFor<TModel, TValue>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TValue>> expression, SelectList selectList)
    {      
      MvcHtmlString label = LabelExtensions.LabelFor(helper, expression, new { @class = "col-md-3 control-label" });
      MvcHtmlString select = SelectExtensions.DropDownListFor(helper, expression, selectList, new { @class = "form-control" });
      MvcHtmlString validation = ValidationExtensions.ValidationMessageFor(helper, expression, null, new { @class = "help-block" });
      StringBuilder innerHtml = new StringBuilder();
      innerHtml.Append(select);
      innerHtml.Append(validation);
      TagBuilder innerDiv = new TagBuilder("div");
      innerDiv.AddCssClass("col-md-9");
      innerDiv.InnerHtml = innerHtml.ToString();
      StringBuilder outerHtml = new StringBuilder();
      outerHtml.Append(label);
      outerHtml.Append(innerDiv.ToString());
      TagBuilder outerDiv = new TagBuilder("div");
      outerDiv.AddCssClass("form-group");
      outerDiv.InnerHtml = outerHtml.ToString();
      return MvcHtmlString.Create(outerDiv.ToString());
    }
  }
}

and in the view

@Html.BootstrapDropDownFor(m => m.CategoryId, new SelectList(ViewBag.Categories, "ID", "CategoryName"))