darkbyte: Thanks for your reply. To check if the dimemsion changes can work when the screen rotates 90 degree or 270 degree(and it's hard to know whether 90 degree or 270 degree).But when I rotates 180 degree, I dont know what to do. like: 1024 x 768 ------ 0 degree or 180 degree 768 x 1024 ------ 90 degree or 270 degree How to deffer them if they are the same dimension?

Now I need to response to the rotating of my screen. that is , an application made by third-party rotates the screen in a random time, when the screen rotates, I need to do sth.(like pop up a message box). I think I can use a work thread to monitor the changes on screen. but how can I know whether the screen rotated? thanks.

I've resolved the problem. it was Init_guid.h havent been included.

I am a learner and I ve got a COM. I try to learn the structure of the COM, and then did three steps to add a function to the COM and its Interface: 1. In DECLARE_INTERFACE_(ITest4, IUnknown), I added a fuction like this: STDMETHOD(ChangeTest) (THIS_ int nToBeChanged ) PURE; 2. In the CTest4 declaration I added: STDMETHODIMP ChangeTest(int nToBeChanged); 3. In the CTest implement I appended : HRESULT CNvRender::ChangeTest(int nToBeChanged) { m_nChangeNo = nToBeChanged; ::MessageBox(NULL, "fasdf", "hehe",MB_OK); return 0; } 4. register it and get the interface pointer in my file: ITest4 *p; ......(get the pointer p and check it whether it is valid) p->ChangeTest(2); and here the problem arise: Access Violation What's wrong with it ? I need your help.

I registered a COM named "red.ax", and then 1. DEFINE_GUID 2. add the red.lib into the 'link' page 3. CoCreateInstance it. but it get error when linking: hehefaintDlg.obj : error LNK2001: unresolved external symbol _CLSID_NvRender4 is it has something to do with the .lib ? How could I get through it?

I had inserted a Activex control into my project, and put it on one of my dialog(id: IDD_DIALOG1), then I deleted it (the class declearation file and implement file and the control on the dialog).The problem comes out: error C2065: 'IDD_DIALOG1' : undeclared identifier but please note: I checked my resources and verified that the dialog(IDD_DIALOG1) is right there. what have I deleted by mistake?

I used Ms DataGrid to show some data from a table. the connection is successful,but I failed to change the value after double-click the cell. I think maybe the property of the datagrid should be correctly set ,but I dont know which. could anyone so kind to help me?

yeah, I thought there must be sth wrong with the function OnSetfocusEDITap1,I thought may be there is a function named OnGetFocus...., but I failed to find it. Have you met this question?

but there's no message like GetFocus, (I look it up in class wizard)

I dont know how to use it ,can you give me a instance?? thanks a lot!!:confused: