How does a MarkupExtension get to the VisualTree?

Does anyone know how markup extensions like RelativeSource get access to the
visual tree in their ProvideValue implementations?

I want to write a markup extension that walks the tree upward until it finds
an element with a specified Name but I don't see how I can get to the tree or
even the element the markup extension is being invoked on (which is inside a
template).

I've got a scenario where I need to bind to an ancestor just like the
RelativeSource markup extension allows but I can't do it based on the Type of
the ancestor, I need to do it based on the Name of the ancestor. This is
because the item binding is in a template that is hosted in one of several
different parent templates -- and they each will have an element with the
proper Name but the types differ.

Here's a set of links that will give you some more details on Markup
extensions:

Sample of MarkupExtension taking in a FrameworkElement
http://forums.microsoft.com/MSDN/Sho...72475&SiteID=1

NameReferenceExtension - MarkupExtension to do name references
http://rrelyea.spaces.live.com/Blog/...5FE!2260.entry

ServiceProvider and XAML: type converters and markup extensions
http://rrelyea.spaces.live.com/Blog/...5FE!1652.entry

I would say it will be a challenging task starting walking the
visual/logical tree from a markup extension. But you can try using the
FrameworkElement target as an entry point for your tree traversal.

"tbrummel" wrote: