通过WM_GETTEXT获取文本框内容
char sUserName[255];
WPARAM wParam = sizeof(sUserName);
LPARAM lParam = (LPARAM) sUserName;
memset (sUserName, 0, sizeof(sUserName));
SendMessage(this->_hwndEditUserName, WM_GETTEXT, wParam, lParam);
MessageBoxA(0, sUserName, "cugo Log On" ,MB_OK);