1.
      void MyTreeCtrl::PopulateElementNode(wxTreeItemId &id)
   2.
      {
   3. //adding panel control elements and setting its sizer
   5.//the next two lines do not work .  A MyTreeCtrl  and a MyPanel are children of MyFrame ,which is the top level window. A MyPanel object exists inside    MyTreeCtrl Class.An event on a node in the tree should populate the panel.I am setting a sizer with the panel ,but it does not get set. The sizer for the toplevel frame was set at a different place before this event.
   7.

   8.
              wxBoxSizer *paneltopsizer = new wxBoxSizer(wxVERTICAL);
   9.
              (this->mypanel)->SetSizer(paneltopsizer);
  10.

  11.

  12.
              this->MyListCtrl=new wxListCtrl(this->mypanel,
  13.
                      wxID_LISTCTRL,wxDefaultPosition,wxSize(245,100),wxLC_REPORT);
  14.
              wxButton *Add=new wxButton(this->mypanel,wxID_ADD,wxT("Add"));
  15.
              *Delete=new wxButton(this->mypanel,wxID_DELETE,wxT("Delete"));
  16.
              wxButton *ApplyChanges=new wxButton(this->mypanel,wxID_APPLYCHANGES,wxT("ApplyChanges"));
  17.

  18.
              wxBoxSizer *panelbuttonsizer = new wxBoxSizer(wxHORIZONTAL);
  19.
              panelbuttonsizer->Add(Add,0,wxALL|wxALIGN_RIGHT,5);
  20.
              panelbuttonsizer->Add(Delete,0,wxALL|wxALIGN_RIGHT,5);
  21.
              panelbuttonsizer->Add(ApplyChanges,0,wxALL|wxALIGN_RIGHT,5);
  22.
              paneltopsizer->Add(this->MyListCtrl,1,wxALL|wxEXPAND,10);
  23.
              paneltopsizer->Add(panelbuttonsizer,0, wxALIGN_CENTER_HORIZONTAL|wxALL, 5);
  24.

  25.
      //panel control ends
  26.
      }