Uno doesn’t currently support the TreeView, but it’s expected to land in the v3.1 timeframe. Since UWP (and thus Uno and WinUI) doesn’t support grouping in the CollectionViewSource, we’ve provided an alternative implementation that makes use of Linq’s IGrouping and an ItemTemplateSelector to switch between templates based on whether it’s a Category or an Animal node in the tree. Here is the result of the completed sample: Notice that the HierarchicalDataTemplate’s ItemTemplate property points to this template. In this case, we are interested in displaying the Name property of each Animal. This is all the information we need in order to make a HierarchicalDataTemplate that will display the Category of each animal and specify the animals that belong to it: įinally we need a DataTemplate for the leaf nodes, which specifies how we want the Animal data to be displayed. We can access the name of the group (the property we’re grouping by) by using CollectionViewGroup’s Name property, and we can get to the items that belong to the group through the Items property. When using data binding’s grouping feature, each group of items is wrapped in a CollectionViewGroup object. We can get to this data by binding to the Groups property in ICollectionView: In our scenario, we want to bind to the hierarchy we created with grouping, or in other words, we want to bind to the groups. This property returns the custom view (of type ICollectionView) that CollectionViewSource creates on top of the data collection (where the grouping is applied). When binding to a CollectionViewSource, the Binding object knows to grab the CollectionViewSource’s View property. You can easily imagine that by adding more GroupDescriptions you would end up with a deeper hierarchy. In this particular case it has only one level of groups, and another level with the animals. We now have the data in a hierarchical form. Grouping the Animals by Category is done the same way as in my last sample: I am using the same Animal data source I used in my last post. But what do you do if the data you’re given is not structured hierarchically? In this post, I will show you how to create that hierarchy from a flat list of data items, using the grouping feature of data binding. The TreeView control is great at displaying structured data using the HierarchicalDataTemplate (see Karsten’s blog post on this topic). How to display grouped data in a TreeView Create a new WPF Application in Visual Studio named, "TreeViewDemo".The next post in the series originally written by Beatriz Stollnitz. To demonstrate, we need a sample solution. We'll use data binding in the next instalment of the WPF tutorial. In this article we will concentrate on the first two options. You can define the items in XAML, add them using the Items collection from code, or use data binding. There are three common ways in which you can populate a tree view control. This allows many levels of tree view node to be nested. The Items property holds the child items in the hierarchy, also as TreeViewItems. The displayed information in the tree view control is defined in the TreeViewItem's Header property. TreeViewItem inherits from HeaderedItemsControl. In the case of the TreeView, each object in the Items collection is a TreeViewItem instance that represents a root-level element in the list. This base class provides for a list of items. This inherits much of its functionality from ItemsControl. Tree views are created using the TreeView class. Due to the expansion, a large number of items can be navigated quickly, with minimal use of screen space. The control shows a list of nodes that can be expanded and collapsed in order to show or hide child values. The tree view control is ideal for displaying hierarchical data, with either a single root or many top-level items.
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