COM object (no type library) - how do I access the interface from VB.NET?

[Robin Tucker]

I have a COM object, which implements straightforward ly the IDataObject
interface. It seems this isn't the same IDataObject interface we now have
with .NET. Basically, the COM object implements low level interfaces. It
does not have a type library. We use it freely with our unmanaged C++
projects. What I would like to do is load or create one of these objects in
VB.NET, but I cannot seem to do it.

I've tried:

Dim theObject As Object

theObject = GetObject ( "c:\gas.tgw " ) * gas.tgw is a file-type we
associated with the COM object

but how do I get the IDataObject interface from theObject?

Is it possible to use basic low-level COM interfaces with VB.NET?

Any answers would be much appreciated.

[David Browne]

"Robin Tucker" <r.******@therm oteknix.com> wrote in message
news:bk******** ***********@new s.demon.co.uk.. .

I have a COM object, which implements straightforward ly the IDataObject
interface. It seems this isn't the same IDataObject interface we now have
with .NET. Basically, the COM object implements low level interfaces. It
does not have a type library. We use it freely with our unmanaged C++
projects. What I would like to do is load or create one of these objects in VB.NET, but I cannot seem to do it.

I've tried:

Dim theObject As Object

theObject = GetObject ( "c:\gas.tgw " ) * gas.tgw is a file-type we
associated with the COM object

but how do I get the IDataObject interface from theObject?

Is it possible to use basic low-level COM interfaces with VB.NET?

Sure, you can use the COM interfaces but you need a type library. Then you
need to generate an Interop Assembly.

The type library may be embedded in the dll, or you could create it if you
have the MSIL interface definitions.

David

[Robin Tucker]

So I definately need a type library? There is no way we can generate one
for this program - it implements IDataObject in COM but it isn't an
automation object. I would have thought it would just be a case of finding
the interface using "FindInterfaces ". But obviously not. In this case,
VB.NET can't be properly supporting com I guess, if it only supports objects
with type libs.

"David Browne" <davidbaxterbro wne no potted me**@hotmail.co m> wrote in
message news:O6******** ******@TK2MSFTN GP12.phx.gbl...

"Robin Tucker" <r.******@therm oteknix.com> wrote in message
news:bk******** ***********@new s.demon.co.uk.. .

I have a COM object, which implements straightforward ly the IDataObject
interface. It seems this isn't the same IDataObject interface we now have with .NET. Basically, the COM object implements low level interfaces. It does not have a type library. We use it freely with our unmanaged C++
projects. What I would like to do is load or create one of these

objects in

VB.NET, but I cannot seem to do it.

I've tried:

Dim theObject As Object

theObject = GetObject ( "c:\gas.tgw " ) * gas.tgw is a file-type we
associated with the COM object

but how do I get the IDataObject interface from theObject?

Is it possible to use basic low-level COM interfaces with VB.NET?

Sure, you can use the COM interfaces but you need a type library. Then you
need to generate an Interop Assembly.

The type library may be embedded in the dll, or you could create it if you
have the MSIL interface definitions.

David

[David Browne]

"Robin Tucker" <r.******@therm oteknix.com> wrote in message
news:bk******** ***********@new s.demon.co.uk.. .

So I definately need a type library? There is no way we can generate one
for this program - it implements IDataObject in COM but it isn't an
automation object. I would have thought it would just be a case of finding the interface using "FindInterfaces ". But obviously not. In this case,
VB.NET can't be properly supporting com I guess, if it only supports objects with type libs.

How do the unmanaged C++ programs use this component?

Do they have the interface definitions?
Do they use IDispach?

David

[Robin Tucker]

Something like this - we use CoGetObject - this is part of a method that
gets data from the object and converts it into a DIB for rendering. As you
can see, I may have my work cut-out in VB.NET! (but vb might get ditched if
I cannot do things like this).
// Connect to the object.
IDataObjectPtr image;
TryMethod(CoGet Object(display_ name, 0, IID_IDataObject , (void**)&image) );
// First try to get a DIB.
FORMATETC fe = { CF_DIB, 0, DVASPECT_CONTEN T, index, TYMED_HGLOBAL };
if (SUCCEEDED(imag e->GetData(&fe, &sm)))
{

[Robin Tucker]

We implement the following interfaces on the object:

IClientSecurity
IDataObject
IDispatch
IMarshal
IMultiQI
IOleContainer
IOleInPlaceActi veObject
IOleInPlaceObje ct
IOleItemContain er
IOleObject
IOleWindow
IParseDisplayNa me
IPersist
IPersistFile
IPersistStorage
IProxyManager
IUnknown

"David Browne" <davidbaxterbro wne no potted me**@hotmail.co m> wrote in
message news:%2******** ********@TK2MSF TNGP11.phx.gbl. ..

"Robin Tucker" <r.******@therm oteknix.com> wrote in message
news:bk******** ***********@new s.demon.co.uk.. .

So I definately need a type library? There is no way we can generate one for this program - it implements IDataObject in COM but it isn't an
automation object. I would have thought it would just be a case of

finding

the interface using "FindInterfaces ". But obviously not. In this case,
VB.NET can't be properly supporting com I guess, if it only supports

objects

with type libs.

How do the unmanaged C++ programs use this component?

Do they have the interface definitions?
Do they use IDispach?

David

[Fergus Cooney]

Hi Robin,

Have you tried hauling in your component by adding a Reference to your
project? When I tried that (a long time ago) it said something like "There's
no blah, blah, would you like me to create an Interop wrapper?". Yes please
and off you go. It may not be clever enough to map all your functions but then
again, it may.

Regards,
Fergus
MVP [Windows Start button, Shutdown dialogue]

[Robin Tucker]

No chance! It says it isn't a valid COM component or assembly, which, in a
sense, I guess is true. The component won't show up in the COM tab because
it doesn't have a typelib and it isn't an automation object. My guess is it
just isn't possible and I will either have to create a C++ source file that
will do it for me and somehow links into VB.NET or I will ditch VB.NET and
go back to plain old C++, ATL etc.

"Fergus Cooney" <fi******@tesco .net> wrote in message
news:Or******** ******@tk2msftn gp13.phx.gbl...

Hi Robin,

Have you tried hauling in your component by adding a Reference to your
project? When I tried that (a long time ago) it said something like "There's no blah, blah, would you like me to create an Interop wrapper?". Yes please and off you go. It may not be clever enough to map all your functions but then again, it may.

Regards,
Fergus
MVP [Windows Start button, Shutdown dialogue]

[Fergus Cooney]

Hi Robin,

Shame about that. I'd go the C++ wrapper and then get a .NET wrapper. And
then you can write some wrapper classes around it in VB.NET just so it feels
really warm and cosy. :-)

Go back?? You can't go back. Or maybe I'm just biased.

Best wishes,
Fergus
MVP [Windows Start button, Shutdown dialogue]

[Robin Tucker]

What I don't understand about this situation is the files will happily embed
in Word documents (Insert->Object) - so I must be doing something wrong!

I don't want to go back to C++ - luckily I'm just experimenting with VB.NET
at the start of a project which, after much deliberation, we decided would
be best written in VB.NET. Of course, provided our existing COM components
were compatible. Designing a nice looking UI is a pain in the ass with ATL.
I am going to jump out of the office window if I have to do that.

"Fergus Cooney" <fi******@tesco .net> wrote in message
news:ud******** ******@TK2MSFTN GP12.phx.gbl...

Hi Robin,

Shame about that. I'd go the C++ wrapper and then get a .NET wrapper. And then you can write some wrapper classes around it in VB.NET just so it feels really warm and cosy. :-)

Go back?? You can't go back. Or maybe I'm just biased.

Best wishes,
Fergus
MVP [Windows Start button, Shutdown dialogue]