INFO: MAPI_NO_COINIT Flag To Make MAPIInitialize Not Call CoInit (239853)

MORE INFORMATION

MAPI, by default, will try to initialize COM with a call to CoInitialize. This initializes COM with a single threaded apartment model. Since COM has already been initialized with a multithreaded model and the threading model cannot be changed, MAPIInitialize will fail and return RPC_E_CHANGED_MODE.

If a MAPIINIT_0 structure is passed into MAPIInitialize with ulFlags set to MAPI_NO_COINIT, MAPI will assume that COM has already been initialized and bypass the call to CoInitialize.

As stated before, this flag was added to MAPI in Exchange 5.5 SP1. Attempting to set this flag on earlier versions of MAPI will result in MAPI_E_UNKNOWN_FLAGS, as this flag is not known to previous versions of MAPI.

Steps to Reproduce Behavior

The following code will show the error code and how to use MAPI_NO_COINIT to avoid it:

   //Link in MAPI32.LIB to build this code.
   #define _WIN32_DCOM
   #include <stdio.h>
   #include <conio.h>
   #include <mapix.h>

struct StartOle {
StartOle() { 
      CoInitializeEx(NULL,
         COINIT_MULTITHREADED); 
   }
   ~StartOle() { 
      CoUninitialize(); 
   }
} _inst_StartOle;

   #define MAPI_NO_COINIT 8

void main()
{
   HRESULT hRes;

   MAPIINIT_0 MAPIInit;
   MAPIInit.ulFlags = 
//      MAPI_NO_COINIT | 
      0;
   MAPIInit.ulVersion = MAPI_INIT_VERSION;
   hRes = MAPIInitialize(&MAPIInit);

   MAPIUninitialize();
   if (FAILED(hRes))
   {
      printf("Failed with hRes of %x\n",hRes);		
   }
   printf("Hit any key to continue\n");
   while(!_kbhit()){ Sleep(500);};
	
}
				

Uncomment the line with MAPI_NO_COINIT will clear the error.