type
  TTreehelper = class(TComponent)
  private
    fabc: string;
  published
    property abc: string read fabc write fabc;
  end;
  pTreehelper = ^TTreehelper;

{$R *.dfm}

procedure TForm2.Button1Click(Sender: TObject);
begin
  VirtualStringTree1.LoadFromFile('c:\temp\tree.dat');
end;

procedure TForm2.Button2Click(Sender: TObject);
begin
  VirtualStringTree1.SaveToFile('c:\temp\tree.dat');
end;

procedure TForm2.Button3Click(Sender: TObject);
var
  a: TTreehelper;
begin
  a:=TTreehelper.Create(nil);
  a.abc:='hallo';
  VirtualStringTree1.AddChild(nil, a);
  a:=TTreehelper.Create(nil);
  a.abc:='ballo';
  VirtualStringTree1.AddChild(nil, a);
  a:=TTreehelper.Create(nil);
  a.abc:='callo';
  VirtualStringTree1.AddChild(nil, a);
  a:=TTreehelper.Create(nil);
  a.abc:='dllo';
  VirtualStringTree1.AddChild(nil, a);
end;

procedure TForm2.FormCreate(Sender: TObject);
begin
  VirtualStringTree1.NodeDataSize:=sizeof(TTreehelper);
  RegisterClass(TTreehelper);
end;

procedure TForm2.VirtualStringTree1FreeNode(Sender: TBaseVirtualTree;
  Node: PVirtualNode);
var
  a: TTreehelper;
begin
  a:=TTreehelper(Sender.GetNodeData(node)^);
  a.free;
end;

procedure TForm2.VirtualStringTree1GetText(Sender: TBaseVirtualTree;
  Node: PVirtualNode; Column: TColumnIndex; TextType: TVSTTextType;
  var CellText: WideString);
var
  a: TTreehelper;
begin
  a:=TTreehelper(Sender.GetNodeData(node)^);
  CellText:=a.abc;
end;

procedure TForm2.VirtualStringTree1LoadNode(Sender: TBaseVirtualTree;
  Node: PVirtualNode; Stream: TStream);
var
  a: TTreehelper;
  p: pTreehelper;
begin
  a:=Stream.ReadComponent(nil) as TTreehelper;
  p:=sender.GetNodeData(node);
  p^:=a;
end;

procedure TForm2.VirtualStringTree1SaveNode(Sender: TBaseVirtualTree;
  Node: PVirtualNode; Stream: TStream);
var
  a: TTreehelper;
begin
  a:=TTreehelper(Sender.GetNodeData(node)^);
  Stream.WriteComponent(a);
end;