![]() The source of data is a self-referencing collection of items with the following fields: Id of Item, Name of Item, Id of parent. It steps through all the levels of hierarchy, from top to bottom and adds to each item a collection of its children. Drop a comment or ping us if you're interested in the implementation. The code fills WPF TreeView with a multilevel hierarchical data. The source code associated is available here minus group implementation. Code generation is a good companion in order to take that load out of your hands. We will see in a future post how we can leverage it in order to give a nice refresh to the plain old Model Explorer provided by DSL Tools. While it can be tedious to manually implement this interface for a large number of different types of "nodes". This is certainly an area of investigation in order to provide a better experience for the developer. It would be better to expose a CompositeCollection, however I stopped my investigation when I found out that the property CanFilter of CompositeCollectionView class (returned when CollectionViewSource.GetDefaultView with a CompositeCollection) returns FALSE thus preventing filtering. It’s not optimal to deal with ObservableCollection for InternalChildren property of IFilterableHierarchicalData. Even though the suggested implementation leverages UI virtualization, huge performance improvement can be found when displaying content in a treeview that supports both UI and data virtualization. ![]() Keep in mind that dealing with large numbers of items in the treeview can have a drastic impact on the overall performance. We can extend filtering in order to filter not only based on text input but by type of node or any other criteria. Here is a screenshot of the final result: Return base.SelectTemplate(item, container) Return this.GroupTemplate ? base.SelectTemplate(item, container) Return this.ItemTemplate ? base.SelectTemplate(item, container) Return this.NoGroupingTemplate ? base.SelectTemplate(item, container) Var l_item = (IFilterableHierarchicalData)item Public override DataTemplate SelectTemplate(object item, DependencyObject container) The interesting part is the SelectTemplate method override: The goal of this DataTemplateSelector is to select the appropriate DataTemplate used to display the children of the current node which would be either no grouping at all, a grouping definition or an item. ObservableCollection InternalChildren (=> list of available groups on item) Public interface IFilterableHierarchicalData The later will be bound to the treeview with a HierarchicalDataTemplate. We’ll need an interface that describes the hierarchy (parent and children), how to filter a node (with a Predicate), if a node is filtered (to hook up to the CollectionViewSource filter delegate) as well as the VisibleChildren (children matching the filtering criteria). You got to be able to react if new children have been added.You got to be able to filter the visible children of any node in the hierarchy,.You got to be able to define how you want the filtering to be applied,. ![]() You got to be able to walk the hierarchy both children and parent,.In order to be able to filter a hierarchy you need a few pre requisites: Well, I want to filter user input? Get myself a CollectionViewSource. I have a few rules of thumbs when it comes to developing, if my app needs to be relational I get a relational database, if it needs to communicate I use WCF, if it needs a great UI experience on a desktop application I use WPF. Imagine Windows Explorer, what if you want to see only the folders that contains a particular string and their parents? How would you implement this in WPF? The idea For a while, we have been used to get a few thousands matches in a blink of an eye for any query in your favorite search engine and yet it is not that obvious to filter a hierarchy based on a search input. How would you do that ? Well I am looking at the MVVM or the Model View View Model Pattern, that would be another blog post.As billg mentioned a while back we are in an era where we evolved “from browse to search to subscribe”. Okies now for the next problem, let say i want to display different colors in the tree depending on how the presence of a certain file in the directory. Remember that you have to add the reference to the namespace that you are using at the top of the xaml file, (the xmlns:local=”clr-namespace:TaggerGui”) part ![]() In this case I declare a static public ObservableCollection dirs=new ObservableCollection() in the cs file and bind that using the x:static binding. What you need now is a template or more specifically a HierarchicalDataTemplate that tells the TreeView how to read your object. What I had was a Dir objects that has a List of Directories inside, which i wanted to display in the TreeView I most useful/closest to what I wanted to do was by Mike Hillberg but still its a bit complex for my needs. I have been trying to find some resources for using custom objects as data for WPF TreeView for my own little project. ![]()
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