((CChatClientDlg *)(AfxGetApp()->m_pMainWnd))->m_ButtonSend.EnableWindow()是什么意思？解决方法

((CChatClientDlg *)(AfxGetApp()->m_pMainWnd))->m_ButtonSend.EnableWindow()是什么意思？
((CChatClientDlg *)(AfxGetApp()->m_pMainWnd))->m_ButtonSend.EnableWindow()是什么意思?请高手详细解释一下。
------解决方案--------------------
1:(AfxGetApp()->m_pMainWnd) 获取主对话框指针
2:(CChatClientDlg *)(AfxGetApp()->m_pMainWnd)强制转换成CChatClientDlg *
3:((CChatClientDlg *)(AfxGetApp()->m_pMainWnd))->m_ButtonSend 调用成员变量m_ButtonSend，m_ButtonSend是个窗口对象，从命名看是个按钮
4:((CChatClientDlg *)(AfxGetApp()->m_pMainWnd))->m_ButtonSend.EnableWindow()禁用这个按钮