请参考一些类似的讨论:
从树视图中隐藏树视图根节点 [ ^ ]
在TreeView控件中隐藏根节点 [禁用树视图节点 [从c#中的树视图中删除子节点 [ ^ ]

Refer some similar discussions:
to hide treeview root node from treeview[^]
Hiding root node in TreeView control[^]
disable a treeview node[^]
child node removing from treeview in c#[^]