When I create a "container" page (a page without a template) from admin mode, the icon looks as it is supposed to and this page is not rendered as expected (There is no preview for this page is displayed while edit mode loads).

However, when I create it programmatically, the PreviewBlockController gets called and I get the grey view instead of no view. 

I cannot use BlockData instead of IContentData here (getting the exception):

public class PreviewBlockController : ActionControllerBase, IRenderTemplate<IContentData>

=>

public class PreviewBlockController : ActionControllerBase, IRenderTemplate<BlockData> (this gives an error, as the preview expects a PageData).

Is it possible to use preview page for blocks only and not as default controller?

This is the view:

@using EPiServer.Web.Mvc.Html
@inherits System.Web.Mvc.WebViewPage<EPiServer.Core.IContentData>

@{
    Layout = null;
}

@if(@Model != null) {
    { Html.RenderContentData(@Model, false); }
}

This is the controller:

    [TemplateDescriptor(Inherited = true, Tags = new string[] { RenderingTags.Preview })]
    public class PreviewBlockController : ActionControllerBase, IRenderTemplate<IContentData>
    {
        public ActionResult Index()
        {
            var contentLink = Request.RequestContext.GetContentLink();
            IContentData content = null;
            if (contentLink != null)
            {
                var contentRepo = ServiceLocator.Current.GetInstance<IContentRepository>();
                content = contentRepo.Get<IContentData>(contentLink);

                if (!(content is SiteBlockData)) return null;
            }

            return View(content);
        }
    }