Use VB-DLL in C

Hi GURU,

I am just wondering, is it possible to use VB-DLL in C (not C++).

I have tried to look at: http://msdn.microsoft.com/library/de...uion020298.asp
but there is no sample code how to use DLL or COM object in C (not C++).

If it is possible to use VB-DLL in C, is there any sample codes that I could look at?

Thanks for any help in advance...

Cheers :)

Quote:

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Originally Posted by ryu

but there is no sample code how to use DLL or COM object in C (not C++).

If it is possible to use VB-DLL in C,

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As far as I know .. No, it's not possible..
C is not an Object oriented language..
COM is based on Object orientation.
And VB does not create standard DLLs..It creates COM components.

Quote:

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Originally Posted by hspc

VB does not create standard DLLs..It creates COM components.

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you can create normal DLL in VB with the
Compile Controller : http://johnchamberlain.com/ccupdates.html
i use it a lot because i hate activex dll and i like api

use this when the function return a string

Code:

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Public Function VBSTOCS(ByVal var1 As String) As String
  VBSTOCS = StrConv(var1, vbFromUnicode)
End Function

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and use this when the function receive a string

Code:

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Public Function CSTOVBS(ByVal var1 As String) As String
  CSTOVBS = StrConv(var1, vbUnicode)
End Function

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example :

Code:

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Public Function Trim2(ByVal cStringPtr As String) As String
  Dim t As Long, z As Long, cString As String
  cString = CSTOVBS(cStringPtr)

'  ... more code go here ...

  Trim2 = VBSTOCS(cString)
End Function

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Hi sergelac,

I not really sure how to call the DLL from C. Can you explain a little bit more? Thanks...

Cheers :)

Quote:

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Originally Posted by hspc

COM is based on Object orientation.

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COM can be accessed by C programs, afterall the Win32 api functions are all written in C, not C++. Granted, its more difficult to do, but it can be, and has been lots of times, done in C.

Quote:

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Originally Posted by ryu

Hi sergelac,

I not really sure how to call the DLL from C. Can you explain a little bit more? Thanks...

Cheers :)

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you might start by checking out the documentation about BSTR and VARIANT structure. All VB variables are really VARIANTs, which is just a union of a bunch of data types, and used as the basic object to pass data between COM objects and VB.

also study articles about mixed-language programming

Quote:

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Originally Posted by stober

COM can be accessed by C programs, afterall the Win32 api functions are all written in C, not C++. Granted, its more difficult to do, but it can be, and has been lots of times, done in C.

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This is new to me..
I can't fugure out how C can call IUnknown members (for example) which are necessary..
any samples ?

Also Win32 api functions are not based on COM !!

Quote:

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Originally Posted by hspc

This is new to me..

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Welcome to real world. :)

Quote:

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I can't fugure out how C can call IUnknown members (for example) which are necessary..
any samples ?

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Sure. See attachment.

Hi Igor,

The COM that you wrote is in C, is that right? If the COM that been wrote in C++, how are you going to call that C++ COM from C?

Another question is that possible to call VB ActiveX or VB DLL from C (not C++)? If yes, how to do it? Could you please provide sample code?

Thanks for any help again in advance...

Cheers :)

Try should check this out along with the BSTR and VARIANT types


http://msdn.microsoft.com/archive/?u...intro_4ar3.asp

Hi Stober & Grogmaster, thanks for the links :)

Cheers...

Quote:

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Originally Posted by ryu

Hi Igor,

The COM that you wrote is in C, is that right?

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No, it's not, the component was written in C++ (ATL) and used in C.

Quote:

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If the COM that been wrote in C++, how are you going to call that C++ COM from C?

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Didn't you noticed? I'm not going to call - I call it. :)

The bitter truth about COM is that it's language independent both for component building and component usage.
In fact ActiveX could be written in any language which supports ActiveX creation as well as it coud be used in any language which supports ActiveX usage. Some languages have both abilities (C, C++, VB, etc.) and some have not (only usage support - scripting languages).
Cross-language usage is possible due to the number of strict rules which component should obey. The topic is really huge, it's not for forum's 'chatting about'.

Quote:

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Another question is that possible to call VB ActiveX or VB DLL from C (not C++)? If yes, how to do it? Could you please provide sample code?

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The answer to first question is - Yes.
About how to do it - you just build AX, register it, extract IDL from its TLB, compiles the latter with MIDL and use it as I explained before, in previous sample.
About 'provide sample code' - frankly saying I hate VB, but I have no choice and use it sometimes. Preparing this sample (see attach) I biult VB ActiveX for the very first time, so please excuse me for its simplicity.

Some tricks used in sample:

1. Build VB project (no tricks!) and register it: regsvr32 vbsimp.dll
2. Open ActiveX with OleView (command line: oleview vbsimp.dll) and copy text of IDL (it must be TypeLib Viewr on top, see right pane) and save it into csimptest directory as vbsimp.idl
3. Use make.bat for C-project building. It could be failed if you don't have VC directory in the PATH - in this case you have to choose: either create new C-project in VC (and use line with midl in PreBuild step) or add to make.bat first line where you have to call vcvars32.bat from your VC like this:

Code:

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call "D:\Microsoft Visual Studio .NET 2003\Vc7\bin\vcvars32.bat"

@midl vbsimp.idl /win32 /h vbsimp.h
@cl csimptest.c ole32.lib user32.lib

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4. Optionally you could make yourself sure our VB ActiveX could be used as it is in JavaScript source, use jssimptest.js.

Beware of VB - it reassign _VBSimp IID for every build, therefore all other steps should be repeated to make component work well.

Hi Igor,

You rocks... It works!!! Thanks GURU!!!!

Cheers :)

PS.
By the way, how do you pass the String into VB? Can I do:

Code:

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typedef wchar_t* BSTR

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If yes, how to translate the BSTR returned by VB? (Since I can not use _bstr_t to do conversion from BSTR to char*)

Quote:

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Originally Posted by ryu

By the way, how do you pass the String into VB?

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Let's add new method to VBSimp...

Code:

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Public Sub NotSoFoo(ByRef strOut As String)
    strOut = "Some string out from VBActiveX"
End Sub

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(VB hides COM type processing - regular String type arrives to subroutine.)

Quote:

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If yes, how to translate the BSTR returned by VB? (Since I can not use _bstr_t to do conversion from BSTR to char*)

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...and call it at C-side

Code:

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BSTR szOutString = SysAllocStringLen( NULL, 260 );
if( SUCCEEDED(pvbs->lpVtbl->NotSoFoo( pvbs, &szOutString ) ) )
{
    char szStr[260];
    // convert string from wide chars (BSTR) to ANSI (CP_ACP)
    WideCharToMultiByte( CP_ACP, 0, szOutString, -1, szStr, sizeof(szStr), 0, 0 );
    MessageBox( NULL, szStr, "Got from ActiveX", MB_OK );
}
SysFreeString( szOutString );

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Have fun. ;)

Thanks Guru Igor...

It works perfectly!!! Can I have a piece of your brain ;)

Cheers... :)

Igor Vartanov ,

This is very very good post .....

And will be highly appreciated , I have a suggestion for you …well this chain of post can be turn in to a very nice Article .

Regards
x8086