C# WPF - Adding a child node to a selected node in

Question

In WPF treeview control, I need to add a child node to a parent node i select using mousedoubleclick event.

http://msdn.microsoft.com/en-us/library/system.windows.controls.treeview.selecteditem.aspx

I followed the step in the MSDN, but i get invalidCastException when i do this.

TreeViewItem newChild = (TreeViewItem)treeView1.SelectedItem;

How can i solve this?

Thanks

Answer 1

What type of Items do you Add() to the Tree? The same type will be returned.
If it is mixed, use

TreeViewItem newChild = treeView1.SelectedItem as TreeViewItem;
if (newChild != null) { ... }

Answer 2

SelectedItem returns the selected data item, not the visual representing it.

If you need to access the selected TreeViewItem, use the ItemContainerGenerator :

TreeViewItem item = treeView1.ItemContainerGenerator.ContainerFromItem(treeView1.SelectedItem) as TreeViewItem;

Not sure it works for nested items though... you might have to use the ItemContainerGenerator of the parent TreeViewItem, which wouldn't be very convenient

EDIT: just tested, indeed it only works for root nodes...

Anyway, the best way to add a node is to use bindings and HierarchicalDataTemplates. You just need to add the object to the data source, and the corresponding TreeViewItem will be added automatically (provided the containing collection implements INotifyCollectionChanged...)