Re: Calling COM functions using IDispatch->Invoke(...

From:
"Alf P. Steinbach" <alfps@start.no>
Newsgroups:
microsoft.public.vc.mfc
Date:
Tue, 22 Apr 2008 23:53:26 +0200
Message-ID:
<yIqdnXyc2LjFw5PVnZ2dnUVZ_v7inZ2d@comnet>
* Alf P. Steinbach:

* Alex:

Alf,
I tried to implement your class,
But it also fails, could you please check out what I?m doing wrong:

SomeCOMObject pComObj; //of course I?ve changed in the constructor
                                           //PROG ID

alfs::DispatchParams dp( 2 );

DISPPARAMS* pDispParam = dp.ptr();

pDispParam->cArgs = 2;
pDispParam->cNamedArgs = 0;


Uh huh. You shouldn't do anything with the innards of the parameters
object. But as it happens it looks like the above does nothing, just
assigning the values that are already there.

Simply don't do anything.

DISPID dispidNamed = DISPATCH_METHOD;
pDispParam->rgdispidNamedArgs = &dispidNamed;


Oops.

Simply don't do anything.

//or
pDispParam->rgdispidNamedArgs = NULL
//as Sven suggested


This is also bad.

Simply don't do anything.

pDispParam->rgvarg = new VARIANTARG[ 2 ];

pDispParam->rgvarg[ 0 ].vt = VT_ERROR;
pDispParam->rgvarg[ 0 ].lVal = DISP_E_PARAMNOTFOUND;

pDispParam->rgvarg[ 1 ].vt = VT_BSTR;
pDispParam->rgvarg[ 1 ].bstrVal = SysAllocString( L"C:\\Program Files\
\... " );


Ditto, simply don't do anything.

Instead,

  dp.setParam( 0, L"Start" );


Sorry, I meant

   dp.setParam( 0, L"\C:\\Program Files\..." );

You might need to quote that path since it contains spaces.

pComObj.call( L"Start", dp );


Cheers, & hth.,

- Alf

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