NodeMouseClick event doesn't work correctly?

i use a treeview to display files and folders like Windows Explorer. it has a NodeMouseClick event but sometimes when i click +, this event doesn't fire.

private void treeView1_NodeMouseClick(object sender, TreeNodeMouseClickEventArgs e)
    {            
        MessageBox.Show("node mouse click");            
 开发者_运维技巧   }

can anyone explain for me why ? and how to know whenever i click + ?

thanks in advance!

---

You might rather want to have a look at

TreeView.AfterExpand Event

Occurs after the tree node is expanded.

or

TreeView.BeforeExpand Event

Occurs before the tree node is expanded.