private void tvBooks_NodeMouseClick(object sender, TreeNodeMouseClickEventArgs e)
{
TreeNode tn = e.Node;
if (tn.Level == 1 && tn.Nodes.Count == 0)
{
foreach (Book book in BookManage.getBooksByGenId(int.Parse(tn.Tag.ToString())))
{
TreeNode btn = new TreeNode(book.Name);
btn.Tag = book.Id;
tn.Nodes.Add(btn);
}
}
}
