I'm new to win32 API programming and I try to understand source code of treeview from codeproject.

But I really don't understand this :

BOOL TreeView::DoNotify(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    // blah blah
    HTREEVIEW Selected = (HTREEITEM)SendDlgItemMessage(hWnd,ID_TREE,TVM_GETNEXTITEM,TVGN_CARET,(LPARAM)Selected);
    // halb halb
}

It doesn't work ( Selected is used without initializing) until I declare Selected as global variable.

Thanks for reading this and I need your help .