I am using the new BlockList to add layout elements to a node. (Inside each layout is another Blocklist which allows users to add blocks of content to the layout area.)

I call the layouts thusly:

    var varBlocks = Model.WContent12;
foreach (var varBlock in varBlocks)
{
    var varBlockContent = varBlock.Content;
    var varBlockSettings = varBlock.Settings;
    string strPartial = "features/" + varBlockContent.ContentType.Alias;
    @Html.Partial(strPartial, varBlockContent);
}

So far, so good.

However, in one particular layout, I wish to add a left navigation automatically. I have done this in other websites and intend to reuse the code. I would normally just use @Html.renderPartial("leftnav") and all would be good.

Except that at this point I am calling the partial from inside the BlockList element. That means I am trying to call IPublishedContent from IPublishedElement.

If I just use the straight renderPartial I get a Cannot bind source type Umbraco.Core.Models.etc... error

I therefore need a method for referring back to the model that called the element, and passing that through in the partial call. Something like: @Html.renderPartial("leftnav", doctypeThatCalledThisElement)

I remember something along these lines using nested content, but it is buried in the codes of time. Any ideas?