first of all Thanku Mr.Doug Forster for ur response.

My scenario is:

      In CMainframe class , I add my own class called CChildWindow
which is derived from CScrollview. In CChildWindow I added my own class
called CPagewindow which is been derived from CFrameWnd.The place where
I get error is , While I am trying to close my main application,
CMainframe's OnClose() is called which in turn calls CChildWindow's
OnClose() where the  Pagewindow->DestroyWindow() is called. Here only
the assertion occurs.

        CMainframe -> CChildWindow -> CPageWindow -> DestroyWindow()

The Code follows as:

void CMainFrame::OnClose()
{

GlobalMembers::m_PageWindowHandle=m_ChildWnd->m_structPgDetails[i].PageHandle;
m_ChildWnd->OnClose();
CFrameWnd::OnClose();

}

void CChildWindow::OnClose()
{
    pagewindow->DestroyWindow();
}

///// Asserts here in destroy window
Debug Assertion Failed!

/////