How to mix databound and static levels in a TreeView?

Question

I have a collection of Database objects, each containing collections of Schema objects and User objects. I want to bind them to a TreeView, but adding

Answer 1

Oh man this is an incredibly frustrating task. I've tried doing it myself many times. I had a very similar requirement where I've got something like a Customer class that has both a Locations collection and a Orders collection. I wanted Locations and Orders to be "folders" in the tree view. As you've discovered, all the TreeView examples that show you how to bind to self-referencing types are pretty much useless.

First I resorted to manually building a tree of FolderItemNode and ItemNode objects that I would generate in the ViewModel but this defeated the purpose of binding because it would not respond to underlying collection changes.

Then I came up with an approach which seems to work pretty well.

• In the above described object model, I created classes LocationCollection and OrderCollection. They both inherit from ObservableCollection and override ToString() to return "Locations" and "Orders" respectively.
• I create a MultiCollectionConverter class that implements IMultiValueConverter
• I created a FolderNode class that has a Name and Items property. This is the placeholder object that will represent your "folders" in the tree view.
• Define hierarchicaldatatemplate's that use MultiBinding anywhere that you want to group multiple child collections into folders.

The resulting XAML looks similar to the code below and you can grab a zip file which has all the classes and XAML in a working example.