MFC 模态对话框与非模态对话框

1 模态对话框与非模态对话框
//1
CChatDlg *pChatDlg = new CChatDlg;        //pChatDlg会被释放
if (FALSE == pChatDlg->Create(IDD_CHAT_DLG, this))
{
    return;
}
pChatDlg->ShowWindow(SW_SHOW);    //不show看不到的

//2 再次点击不能用了

CChatDlg pChatDlg;        //.h
if (FALSE == pChatDlg.Create(IDD_CHAT_DLG, this))
{
    return;
}
pChatDlg->ShowWindow(SW_SHOW);    //不show看不到的

//3
CChatDlg m_ChatDlg;        //.h
if (m_ChatDlg.m_hWnd == NULL)
{
    if (FALSE == m_ChatDlg.Create(IDD_CHAT_DLG, this))
    {
        return;
    }

}
m_ChatDlg.ShowWindow(SW_SHOW);