title: How can I get all expanded nodes in treeview?
body: <p>I have a program that contains a TreeView. All of my nodes except for the root and two nodes under the root are loaded from a database.</p>
  
  <p>When the user adds data to the database it must be automatically added to the TreeView. I can successfully do this by clearing all the nodes, add the default nodes and add all the data including the new one to my TreeView, but all nodes of the new TreeView are collapsed.</p>
  
  <p>Our client wants to retain all expanded nodes but still add the new data he just added. Is there any way to know all expanded nodes and expand it again once collapsed or refreshed? Thank you for any response.</p>