DynamicPlaceholdersWithoutFluentTagBuilder.cshtml

@* Using with a basic TagBuilder *@
@{
    var colDiv = new TagBuilder("div");
    colDiv.AddCssClass("col-sm-4");
    colDiv.GenerateId("featureCol");
}
<div>
    @Html.Sitecore().DynamicPlaceholder("feature", colDiv, 3, 3)
</div>

@* Using with a Func<DynamicPlaceholderRenderContext, TagBuilder> *@
@functions {
    TagBuilder CreateColBuilder(DynamicPlaceholderRenderContext context)
    {
        var builder = new TagBuilder("div");
        builder.AddCssClass("col-sm-" + 12/context.PlaceholdersCount);
        builder.GenerateId("featureCol" + context.Index);
        return builder;
    }
}
<div class="row">
    @Html.Sitecore().DynamicPlaceholder("feature", CreateColBuilder, 3, 4)
</div>