C# TreeView树节点实现部分节点左侧显示CheckBox

#region 隐藏CheckBoxs

    public void treeViewGroupStatements_DrawNode(object sender, DrawTreeNodeEventArgs e)
    {
        HideLevelOfTreeView(e.Node);
        e.DrawDefault = true;
    }
    public void HideLevelOfTreeView(TreeNode tn)
    {
        //TreeNode parNode = tn.Parent;
        //if (parNode != null && parNode.Text == "全部项目")
        //{
        //    HideCheckBox(tn.TreeView, tn);
        //}
        ProjectFolderDTO prjFolderDTO = tn.Tag as ProjectFolderDTO;
        if (prjFolderDTO != null)
        {
            if (!GlobalData.NewPaperSets.Contains(prjFolderDTO.NodeType.ToString()))
            {
                HideCheckBox(tn.TreeView, tn);
            }
        }
        ProjectInfoDTO prjInfoDTO = tn.Tag as ProjectInfoDTO;
        if (prjInfoDTO != null)
        {
            HideCheckBox(tn.TreeView, tn);
        }
    }

    //#endregion
    private const int TVIF_STATE = 0x8;
    private const int TVIS_STATEIMAGEMASK = 0xF000;
    private const int TV_FIRST = 0x1100;
    private const int TVM_SETITEM = TV_FIRST + 63;
    private void HideCheckBox(TreeView tvw, TreeNode node)
    {

        TVITEM tvi = new TVITEM();

        tvi.hItem = node.Handle;

        tvi.mask = TVIF_STATE;

        tvi.stateMask = TVIS_STATEIMAGEMASK;

        tvi.state = 0;

        SendMessage(tvw.Handle, TVM_SETITEM, IntPtr.Zero, ref tvi);

    }

    [StructLayout(LayoutKind.Sequential, Pack = 8, CharSet = CharSet.Auto)]
    private struct TVITEM
    {
        public int mask;
        public IntPtr hItem;
        public int state;
        public int stateMask;
        [MarshalAs(UnmanagedType.LPTStr)]
        public string lpszText;
        public int cchTextMax;
        public int iImage;
        public int iSelectedImage; public int cChildren; public IntPtr lParam;
    }

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern IntPtr SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, ref TVITEM lParam);
    #endregion