WPF Tree List - Control Visibility of Expand Buttons when Sub-level Children are not Fetched

This example demonstrates how to specify whether a child node has children (and should display the expand button) when the TreeListView does not fetch sub-level nodes.

The TreeListView in hierarchical binding mode fetches child nodes of sub-level nodes when you expand their parent node. Such behavior is designed to determine whether to display expand buttons. You can set the TreeListView.FetchSublevelChildrenOnExpand property to false to keep sub-level children unfetched. In this case, all child nodes display expand buttons (even if they do not have children). The expand button is hidden when you expand a node that does not contain child nodes:

Follow the steps below to prevent this behavior:

1. Your data source objects should contain a field that specifies whether an item has children.
2. Assign the field name to the TreeListView.HasChildNodesPath property to display expand buttons only when required.

As a result, the TreeListView does not fetch sub-level children to determine whether to display expand buttons:

Files to Review

• MainWindow.xaml
• ViewModel.cs (VB: ViewModel.vb)

Documentation

• Expand and Collapse Nodes
• TreeListView.HasChildNodesPath
• TreeListView.FetchSublevelChildrenOnExpand
• Bind to Hierarchical Data Structure

More Examples

• WPF Tree List - Control Whether to Create Child Nodes
• WPF Tree List - Implement the Child Nodes Path
• WPF Tree List - Load Nodes Asynchronously Without Locking the Application's UI

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