COM for eMbedded Visual C++ 3.0 ( Under Windows CE )

Environment: eMbedded Visual C++ 3.0, Windows 2000, Windows CE Emulator (Handheld PC Pro)

To Run this application we must have installed eMbedded Visual C++ 3.0

The Generation of the COM Server and the COM Client in embedded Visual C++ 3.0 is somewhat different than the Microsoft Visual C++ 6.0. It leads an error in the COM server while running the client. This Article resolves the error and achieves the Server functionality.

Generate the Server( CEServer.dll)

Generate the work space for the Server.

Step: 1

Step: 2

click finish.

Step 3:

Select Simple Object for the COM. Because we need simple COM object that supports in-proc server.

Click Next to select the interface name

Type Process in the field for short name. It automatically generates the Class name, Interface name etc as it was in Visual C++ 6.0.

Press OK. Now we have given the parameters how the COM object should be.

Build the Server dll. It builds successfully and does not give any error. We have generated the COM Server.

Generate the Client( CEClinet.exe)

Step 1:

Let the Client be a dialog based application,

The Design of the dialog is as shown in the figure.

Step 2:

Add the Server dll file path in stdafx.h file after #endif

#import "C:\\Program Files\\Windows CE Tools\\wce211\\MS HPC Pro
\\emulation\\hpcpro\\windows\\CEServer.dll" no_namespace

Note: In my system, the Windows CE Tools directory is in the Program Files. Try to modify according to your path.

Step 3:

Declare the pointer for the Process interface in the header file CEClientDlg.h,

CLSID clsid;
IProcess *m_pProcess;

Add the following lines in the OnInitDialog in CEClientDlg.cpp,

BOOL CCEClientDlg::OnInitDialog()
{
  CDialog::OnInitDialog();
  // TODO: Add extra initialization here
  HRESULT hr;
  hr = CLSIDFromProgID(OLESTR("CEServer.Process.1"),&clsid);
  if(FAILED(hr))
    MessageBox(NULL,_T("Prog id failed"), MB_OK);
  CoCreateInstance(clsid,
                   NULL,
                   CLSCTX_INPROC_SERVER,
                   __uuidof(IProcess),
                   (void**)&m_pProcess);

  if(m_pProcess == NULL)
    MessageBox(NULL,_T("interface pointer failed"), MB_OK);
  return TRUE; // return TRUE  unless you set the
               // focus to a control
}

Step 4:

Then call the function from the interface while the user clicks the button,
void CCEClientDlg::OnCallServer() 
{
  m_pProcess->Show();
}

Compile the Client Project. You will get some error in the server in the CEServer.tli file.

That is,  error C2065: '_com_issue_errorex' : 
  undeclared identifier.

This is the main difference while creating the COM in eMbedded Visual C++ 3.0. This error does not come in Microsoft Visual C++ 6.0. This article is mainly dedicated to solve this error and run the COM Client Successfully.

What to be done to resolve this problem
(The modification is in the CEServer.dll)

Add the definition or override the existing function.

Step 1:

Goto CEServer.idl file,

interface IProcess : IDispatch
{
   //Show function 
   //Add this function declaration here
   [id(2), helpstring("method _com_issue_errorex")] HRESULT
            _com_issue_errorex(HRESULT _hr1,
                               IUnknown  *pthis1,
                               const GUID  refiid1);
};

Step 2:

Goto Process.h file,

Add the declaration ,

STDMETHOD(_com_issue_errorex)(HRESULT _hr1,
            IUnknown  *pthis1,
            const GUID  refiid1);

Step 3:

Goto Process.cpp file,

Add the definition,

STDMETHODIMP CProcess::_com_issue_errorex(HRESULT _hr1,
            IUnknown  *pthis1,
            const GUID  refiid1)
{
  AFX_MANAGE_STATE(AfxGetStaticModuleState())

  // TODO: Add your implementation code here

  return S_OK;
}

Rebuild all.

Again come to the COM Client and rebuild the client application.

Downloads

Download demo project (COM CE Server) - 30 Kb
Download demo project (COM CE Client) - 40 Kb