What are the valid reasons to use ContentPresenter outside of template?

Question

I stumbled upon an article by Den Delimarsky on What is a ContentPresenter? which says:

In WPF there is an element called ContentPresenter, that is often used inside control templates, as well as inside the root application markup.

I don't understand the "inside the root application markup" part, because I thought that ContentPresenter can only used inside of a ControlTemplate.

The role of the ContentPresenter is quite clear when used in a ControlTemplate, but what are the valid reasons to use ContentPresenter outside of a template's markup?

Answer 1

(This seems to be a quite outdated reply.)

There are valid uses of ContentPresenter everywhere. My primary use of it is to dispatch the view by the runtime type of the content.

Let me explain: imagine that you have a property of type Animal in your VM, so you'd like to display it somewhere in your UI. If you have a single UI for any kind of Animal, you can put it into a UserControl, and use a construct like

<AnimalControl DataContext="{Binding Animal}"/>

However imagine that you've got a bunch of different animals, say, Toads, Humans and Unicorns. So you'd like to differentiate between them (maybe you've developed several UserControls for them). You do it in the following way:

<ContentPresenter Content="{Binding Animal}"/>

In order for the correct view to be used, you need the following DataTemplates to be in scope:

<DataTemplate TargetType="{x:Type vm:Unicorn}">
    <UnicornControl/>
</DataTemplate>

etc. Usually people get such a functionality using TemplateSelector/ContentTemplateSelector, but this way is valid, too, and seems to be simpler (you can shuffle template scopes with custom styles, a la CSS).

Answer 2

There are no reasons. You should use ContentControl rather then ContentPresenter outside of a template.