TreeView в Visual C++

CreateWindowEx(NULL,WC_TREEVIEW,"TreeView",
  WS_VISIBLE | WS_CHILD |WS_BORDER|  TVS_HASLINES | TVS_LINESATROOT | TVS_HASBUTTONS,
  10,50,300,400,hwnd, NULL, hInst, NULL);

VOID AddItemToTree(HWND hwnd, LPSTR lpszItem, int nLevel)
{
TVITEM tvi;
TVINSERTSTRUCT tvins;
static HTREEITEM hPrev = (HTREEITEM)TVI_FIRST;
static HTREEITEM hPrevRootItem = NULL;
static HTREEITEM hPrevLev2Item = NULL;
HTREEITEM hti;
tvi.mask = TVIF_TEXT|TVIF_PARAM;
tvi.pszText = lpszItem;
tvi.cchTextMax = sizeof(tvi.pszText)/sizeof(tvi.pszText[0]);
tvi.lParam = (LPSTR)lpszItem;
tvins.item = tvi;     tvins.hInsertAfter = hPrev;
if (nLevel == 1)         tvins.hParent = TVI_ROOT;
else if (nLevel == 2)         tvins.hParent = hPrevRootItem;
      else         tvins.hParent = hPrevLev2Item;
hPrev = (HTREEITEM)SendMessage(tvwnd,TVM_INSERTITEM,0,(LPARAM)(LPTVINSERTSTRUCT)&tvins);
if (nLevel == 1)         hPrevRootItem = hPrev;
else if (nLevel == 2)         hPrevLev2Item = hPrev;
if (nLevel > 1)     {
hti = TreeView_GetParent(hwnd, hPrev);
tvi.hItem = hPrev;
TreeView_SetItem(tvwnd, &tvi);
}
}

case WM_NOTIFY:
        tv=(LPNMTREEVIEW) lParam;        
            if(tv->hdr.code==TVN_SELCHANGED)
            {
                str = tv->itemNew.pszText;
                               //  ...
                        }