treeview有关问题,怎么在根节点添加子节点

treeview问题,如何在根节点添加子节点
如
a 
  a
  a
  a
b
  b
  b
  b
c
  c
  c
  c
想每按一次按钮就分别在根节点a,b,c
添加
a,b,c


[解决办法]
for I := 0 to treeview1.items.count - 1 do
begin
node := treeview1.items[i];
if (node.text = 'a') and (node.Level = 0)then
begin
TreeView1.Items.AddChildFirst (node,'a');
end ;
if (node.text = 'b') and (node.Level = 0)then
begin
TreeView1.Items.AddChildFirst (node,'b');
end ;
if (node.text = 'c') and (node.Level = 0)then
begin
TreeView1.Items.AddChildFirst (node,'c');
end ;
end ;

[解决办法]

Delphi(Pascal) code

var  i: Integer;  Node: TTreeNode;begin  for i := TreeView1.Items.Count - 1 downto 0 do  begin    Node := TreeView1.Items[i];    if Node.Level = 0 then      TreeView1.Items.AddChild(Node, Node.Text);  end;end;