一种限制MFC MDI架构中某类型文档个数的方法

void CtestmdiApp::OnFileNew()
{
    POSITION pos = m_pDocManager->GetFirstDocTemplatePosition();

    while (pos != NULL)
    {
        CDocTemplate* pDocTemp = m_pDocManager->GetNextDocTemplate(pos);
        POSITION docPos = pDocTemp->GetFirstDocPosition();

        while(docPos != NULL)
        {
            CDocument* pDoc = pDocTemp->GetNextDoc(docPos);
            if (pDoc->IsKindOf(RUNTIME_CLASS(CtestmdiDoc)))
            {
                return;
            }
            break;
        }

    }
    CWinAppEx::OnFileNew();
}