I've already test it. Use the namespaces as well. But no luck. Amazing thing is,

Code:
		if(m_rtfCtrl.CreateEx(WS_EX_APPWINDOW, WS_BORDER|ES_MULTILINE, CRect(10,10,200,200), &x , 1))
		{
			CString ss;
			CFile rtfFile;
			BOOL err = rtfFile.Open("G:\\Work On\\CPP\\RTFControl\\TestFile.rtf", CFile::modeReadWrite, NULL);

			int iLength = rtfFile.GetLength();// Data length
			char *pBuffer = new char[iLength];// Data buffer

			rtfFile.Read(pBuffer, iLength);
			CString rtf(pBuffer);

			m_rtfCtrl.SetWindowText(rtf);
			m_rtfCtrl.GetWindowText(ss);

			std::cout << ss << std::endl;

			// CString into string
			std::string strRTF(ss.GetString());
			

			std::cout << strRTF << std::endl;

		}
In my above code, fist cout works fine. The second cout not works.