Installing a MAPI filter

I recently came across the challenge of writing an application that processed SMS messages. The MAPIRULE sample of the Pocket PC 2003 was duly studied, successfully modified and used. The real challenge came when I needed to cleanly install it and uninstall it. Installing is simple: you just copy the DLL to the \Windows folder, register it (the setup can do this for you) and then you have to soft-reset the device (a setup DLL is required for this). This is quite simple and a sample of soft-reset code can be found here.

Uninstalling calls for a different approach. First, you have to make sure that the DLL is not being used by the SMS-handling process. My answer to this is to shut down the tmail.exe process. Here is some code:

BOOL KillProcess(LPCTSTR pszProcName)
{
  HANDLE hSnapshot;
  BOOL   bRet  = FALSE;
  
  hSnapshot = CreateToolhelp32Snapshot(
               TH32CS_SNAPPROCESS, 0);
  if((int)hSnapshot != -1)
  {
    BOOL           bOk;
    PROCESSENTRY32 pe;
    DWORD          dwID = 0;
    HANDLE         hProcess;

    pe.dwSize = sizeof(PROCESSENTRY32);

    for(bOk = Process32First(hSnapshot, &pe); 
        bOk; 
        bOk = Process32Next(hSnapshot, &pe))
    {
      if(!wcsicmp(pe.szExeFile, pszProcName))
        dwID = pe.th32ProcessID;
    }
    CloseToolhelp32Snapshot(hSnapshot);

    if(dwID != 0)
    {
      // Kill the process
      hProcess = OpenProcess(0, FALSE, dwID);
      if(hProcess != INVALID_HANDLE_VALUE)
      {
        bRet = TerminateProcess(hProcess, 0);
        CloseHandle(hProcess);
      }
    }
  }
  return bRet;
}

After killing the process, you have to unregister the DLL (sample code here) and finally soft-reset the device.

A sample setup dll project is available on demand.