Autosize witdth of treeview after collapse

Question

Greetings,

I'm looking for a way to set the width of a treeview to either it's max, or to the size of the longest treenode in it, whenever a node is being collapsed or opened.

I've tried using the clientsize.. but that doesn't seem to work. Is there a different way to check which node is the longest and set the TreeView.Width to that size?