Grouping child objects in WPF TreeView

Question

I am trying to get my tree view to group a collection of similar items by what they are. To keep things generic, my object hierarchy could look like this:

• Objects
  • Object Group #1
    • Item #1 (Type 'A')
    • Item #2 (Type 'A')
    • Item #3 (Type 'B')
    • Item #4 (Type 'B')

Right now my TreeView shows these objects exactly like the object model, but what I would like to do is insert a TreeView node for each object type so that it would look like this:

• Objects
  • Object Group #1
    • Type A
      • Item #1
      • Item #2
    • Type B
      • Item #3
      • Item #4

I saw in a similar question here that someone recommended to have two separate HierarchicalDataTemplates so I created one for 'Object Group #1' level which contains a TreeView with a list of the types, but this is really clumsy since it is a whole separate TreeView inside of some nodes. I have also been trying to use a CollectionViewSource to filter out the items in each category, but this doesn't do me very much good since I can't figure out how to display them.

I guess my question boils down to this: How do I make a HierarchicalDataTemplate group it's children? If someone could point me in the right direction I would appreciate it a lot.

I can post some code if anyone wants to see, but I am really just trying to figure out how to do what I want so my code is just a pretty straight forward databound treeview right now.

Answer 1

Take a look at this article by Mr. Sumi. I'm sure it will help you.

The gist of the article:

My solution to that very problem requires the following ingredients:

• A MultiBinding that allows you to combine different bindings.
• A converter that helps us organizing the different bound collections into sub folders, where necessary.
• And of course: Data templates that provide a visual representation of your bound data.