Passing a structure from VB to an ActiveX control

[Jeff Yoder]

I'm trying to pass a structure from VB to an ActiveX control written in Visual
C. I've defined the data type of the structure in an idl library, and VB
recognizes it as a valid data type. I can declare variables of that type
in VB and use them. On the C side, I can use the structure as well. Where
I'm running into problems is in figuring out how to pass the structure from
VB to C. Specifically, I can't figure out what needs to be entered into
the DISP_PROPERTY_EX() macro for the final parameter, vtPropType which specifies
the properties type. Anybody tried doing this before?

Thanks,

Jeff

[Boris Karadjov]

You should use VT_VARIANT in DISP_PROPERTY_EX() . The variant set should be
of type VT_RECORD. The following fields of the VARIANT are used:
V_RECORDINFO(&var) contains a pointer to IRecordInfo
(http://msdn.microsoft.com/library/de...dk/automat/cha
p12_69wl.htm) interface. V_RECORD(&var) contains a pointer to the record
data. To make a local copy of the record (structure) use
V_RECORDINFO(&var)->CopyRecord(V_RECORD(&var), &mystruct). Note that
mystruct must be zeroed before a pointer to it being supplied to CopyRecord
method.
--
Boris Karadjov
Brainbench MVP for Visual C++
http://www.brainbench.com

"Jeff Yoder" <jeff.yoder@americanhofmann.com> wrote in message
news:3b05337c$1@news.devx.com...
>
> I'm trying to pass a structure from VB to an ActiveX control written in
Visual
> C. I've defined the data type of the structure in an idl library, and VB
> recognizes it as a valid data type. I can declare variables of that type
> in VB and use them. On the C side, I can use the structure as well.
Where
> I'm running into problems is in figuring out how to pass the structure
from
> VB to C. Specifically, I can't figure out what needs to be entered into
> the DISP_PROPERTY_EX() macro for the final parameter, vtPropType which
specifies
> the properties type. Anybody tried doing this before?
>
> Thanks,
>
> Jeff

[Jeff Yoder]

Thanks, Boris,

Do I need to use the CopyRecord function to make the copy? I've been successfully
getting a copy of the record just by dereferencing the pointer to the record
data.

Jeff

"Boris Karadjov" <bbmvp@cpppp.virtualave.net> wrote:
>You should use VT_VARIANT in DISP_PROPERTY_EX() . The variant set should
be
>of type VT_RECORD. The following fields of the VARIANT are used:
>V_RECORDINFO(&var) contains a pointer to IRecordInfo
>(http://msdn.microsoft.com/library/de...dk/automat/cha
>p12_69wl.htm) interface. V_RECORD(&var) contains a pointer to the record
>data. To make a local copy of the record (structure) use
>V_RECORDINFO(&var)->CopyRecord(V_RECORD(&var), &mystruct). Note that
>mystruct must be zeroed before a pointer to it being supplied to CopyRecord
>method.
>--
>Boris Karadjov
>Brainbench MVP for Visual C++
>http://www.brainbench.com
>
>"Jeff Yoder" <jeff.yoder@americanhofmann.com> wrote in message
>news:3b05337c$1@news.devx.com...
>>
>> I'm trying to pass a structure from VB to an ActiveX control written in
>Visual
>> C. I've defined the data type of the structure in an idl library, and
VB
>> recognizes it as a valid data type. I can declare variables of that type
>> in VB and use them. On the C side, I can use the structure as well.
>Where
>> I'm running into problems is in figuring out how to pass the structure
>from
>> VB to C. Specifically, I can't figure out what needs to be entered into
>> the DISP_PROPERTY_EX() macro for the final parameter, vtPropType which
>specifies
>> the properties type. Anybody tried doing this before?
>>
>> Thanks,
>>
>> Jeff
>
>

[Boris Karadjov]

Well, if the record does not contain BSTRs, interface pointers, VARIANTs,
SAFEARRAYs, etc. or if you do not need to make a copy of the record you can
skip the call to CopyRecord.
--
Boris Karadjov
Brainbench MVP for Visual C++
http://www.brainbench.com


"Jeff Yoder" <jeff.yoder@americanhofmann.com> wrote in message
news:3b09055a@news.devx.com...
>
> Thanks, Boris,
>
> Do I need to use the CopyRecord function to make the copy? I've been
successfully
> getting a copy of the record just by dereferencing the pointer to the
record
> data.
>
> Jeff
>
> "Boris Karadjov" <bbmvp@cpppp.virtualave.net> wrote:
> >You should use VT_VARIANT in DISP_PROPERTY_EX() . The variant set should
> be
> >of type VT_RECORD. The following fields of the VARIANT are used:
> >V_RECORDINFO(&var) contains a pointer to IRecordInfo
>
>(http://msdn.microsoft.com/library/de...sdk/automat/ch
a
> >p12_69wl.htm) interface. V_RECORD(&var) contains a pointer to the record
> >data. To make a local copy of the record (structure) use
> >V_RECORDINFO(&var)->CopyRecord(V_RECORD(&var), &mystruct). Note that
> >mystruct must be zeroed before a pointer to it being supplied to
CopyRecord
> >method.
> >--
> >Boris Karadjov
> >Brainbench MVP for Visual C++
> >http://www.brainbench.com
> >
> >"Jeff Yoder" <jeff.yoder@americanhofmann.com> wrote in message
> >news:3b05337c$1@news.devx.com...
> >>
> >> I'm trying to pass a structure from VB to an ActiveX control written in
> >Visual
> >> C. I've defined the data type of the structure in an idl library, and
> VB
> >> recognizes it as a valid data type. I can declare variables of that
type
> >> in VB and use them. On the C side, I can use the structure as well.
> >Where
> >> I'm running into problems is in figuring out how to pass the structure
> >from
> >> VB to C. Specifically, I can't figure out what needs to be entered
into
> >> the DISP_PROPERTY_EX() macro for the final parameter, vtPropType which
> >specifies
> >> the properties type. Anybody tried doing this before?
> >>
> >> Thanks,
> >>
> >> Jeff
> >
> >
>