Add ChildItem to TreeView's SelectedItem

Question

I have a TreeView in my WPF application. The user can create categories in this TreeView. Now I want to add an Item to the selected item of the Treeview. How do I add a childItem to the selected item in a Treeiew?

The following code doesn't work, how can I go about fixing this?

The current code I have:

if (treeViewCategories.SelectedItem != null)
{
    //Unable to cast the SelectedItem to a TreeViewItem('System.String' to 'System.Windows.constrol.TreeViewItem)
    TreeViewItem selectedItem = (TreeViewItem)treeViewCategories.SelectedItem;
    selectedItem.Items.Add(pictureList[counter]);
}

Answer 1

TreeView in WPF has a property called SelectedItem.

TreeViewItem selectedTVI = (TreeViewItem)myTreeView.SelectedItem;
selectedTVI.Items.Add(newChild);

You should read the documentation. SelectedValue is the "value of the property that is the specified by SelectedValuePath for the SelectedItem", not the actual SelectedItem which I've shown above.