How to force gtktree always select a node?

[mili <milimeter 163 com>]

Hello, everybody

  You know, if a sub node of GtkTreeView is selected, and then I callapse its 
parent node, then the whole tree lost selection. Now, I want to force my tree 
to select one node at all the time, how should I do?

  And who knows how to change GtkTreeView expander style to traditional +/- 
tree style?

  And the third question, How to add grid line to GtkTreeView? I want to make 
my data displayed in list more neaty and more clear.

  Thanks,