Customizing a Runtime Callable Wrapper

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Ruxo Zheng - 19 Sep 2003 09:19 GMT

I've tried to customize the Execute method of ADO Command from its
generated DLL (by Tlbimp.exe). The original code of the Execute method
is:

.method public hidebysig newslot virtual
instance class msado27.Recordset
marshal( interface)
Execute([out][opt] object& marshal( struct) RecordsAffected,
[in][opt] object& Parameters,
[in][opt] int32 Options) runtime managed internalcall
{
.custom instance void [mscorlib]
System.Runtime.InteropServices.DispIdAttribute::.ctor(int32) = ( 01 00 05
00 00 00 00 00 )
.param [3] = int32(0xFFFFFFFF)
.override msado27._Command::Execute
} // end of method CommandClass::Execute

I want to change the second argument to be int32 type without
referencing. But just changing the type only causes the exception:

"Could not load type msado27.CommandClass from assembly msado27, Version=
2.7.0.0, Culture=neutral, PublicKeyToken=null."

What I have to do more to make it work? Can I create an another overload
method instead?

Thanks ...
Ruxo

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Mattias Sj?gren - 19 Sep 2003 10:08 GMT

Ruxo,

>I want to change the second argument to be int32 type without
>referencing.

Why? I wouldn't expect that to work.

> But just changing the type only causes the exception:
>
>"Could not load type msado27.CommandClass from assembly msado27, Version=
>2.7.0.0, Culture=neutral, PublicKeyToken=null."

If you catch that exception and look for an inner exception, it might
tell you more about why it fails.

You have to make sure you have matching declarations of the method in
both in the _Command interface and in the CommandClass class.

>Can I create an another overload method instead?

No

Mattias

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Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/
Please reply only to the newsgroup.

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Ruxo Zheng - 22 Sep 2003 03:20 GMT

Thanks Mattias for your clarification.

My original intention is to make the Execute method of ADO Command to
take no arguments. So I can migrate my VB6 code into .NET without
problems. (Or at least, I can really pass NULL value -- zero -- for the
second argument.)

But since .NET doesn't support [Optional] attribute. So I though about
two solutions. That's either changing the argument or overloading with a
new Execute method.

If both solutions can't work anyway, what to do if we find another legacy
COMs that use similar optional arguments? Is this a limit of .NET interop
for COM components?

Ruxo

> Ruxo,
>
>>I want to change the second argument to be int32 type without
>>referencing.
>
> Why? I wouldn't expect that to work.

<<-- old message is snipped -->>

> Mattias

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Mattias Sj?gren - 22 Sep 2003 20:57 GMT

>But since .NET doesn't support [Optional] attribute.

VB.NET has full support for optional parameters.

In other languages such as C# you at least have the ability to make a
COM imported VARIANT parameter look unspecified to the callee, like
this

http://www.dotnetinterop.com/faq/?q=MissingOptional

>So I though about
>two solutions. That's either changing the argument or overloading with a
>new Execute method.

Neither will work, sorry.

Mattias

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Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/
Please reply only to the newsgroup.

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Ruxo Zheng - 23 Sep 2003 02:50 GMT

Thanks Mattias, this's greatly help! :D

Rux

>>But since .NET doesn't support [Optional] attribute.
>
[quoted text clipped - 7 lines]
>
> Mattias

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Customizing a Runtime Callable Wrapper

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