> I am having trouble with the following scenario....
>
> Assembly A
> Returns a managed implementation of COM IStream interface to the
> unmanaged world
> =============
>
> /////////////////
> [ComImport]
> [GUID("..")]
> interface IStreamAssemblyA
> {
> ..
> }
>
> class MyStreamImpl : IStreamAssemblyA
> {
> .........
> }
>
> IntPtr GetStreamImpl()
> {
> MyStreamImpl obj = new MyStreamImpl();
> IntPtr ret =
> Marshal.GetComInterfaceForObject(obj,typeof(IStreamAssemblyA));
> return ret;
> }
> ///////////////////
>
>
> Assembly B
> Gets and uses a COM IStream interface from the unmanaged world. In
> case the implementation is an unmanaged one, everything works OK. In
> case the implementation is actually from assembly A above (or any
> other managed implementation), the cast fails as shown below.....
> ==========
>
> /////////////////
> [ComImport]
> [GUID("..")]
> interface IStreamAssemblyB
> {
> ..
> }
>
> IntPtr GetStreamFromUnmanagedWorld()
> {
> ..
> }
>
> void UseStream()
> {
> IntPtr streamUnk = GetStreamFromUnmanagedWorld();
>
> object obj = Marshal.GetObjectForIUnknown(streamUnk); // obj is
> actually class MyStreamImpl from assembly A above
>
> IStreamAssemblyB stream = obj as IStreamAssemblyB; // this fails
> becuase of different ".Net type" of obj and stream
> }
> /////////////////
>
>
> The above problem exists becuase .Net does not recognize that even though
> IStreamAssemblyA and IStreamAssemblyB are different ".Net types" they are
> actually COM interfaces imported into .Net and so the cast above should be
> allowed (and QueryInterface should be used internally).
>
> How can I solve this issue? Its not possible to have a common IStream
> declartion becuase AssemblyA and AssemblyB are not related in any way except
> to the extent that assembly B happens to use the managed IStream
> implementation from assembly A.
>
> Any help would be appreciated!
>
> Bob

"TDC" <NOtcarvinSPAM@lycos.com> wrote in message
news:1161874227.477845.301460@k70g2000cwa.googlegroups.com...
> Create AssembyC in which you place IStreamAssemblyCommon and then
> reference that from both A and B.
>
>
> Bob S wrote:
>> I am having trouble with the following scenario....
>>
>> Assembly A
>> Returns a managed implementation of COM IStream interface to the
>> unmanaged world
>> =============
>>
>> /////////////////
>> [ComImport]
>> [GUID("..")]
>> interface IStreamAssemblyA
>> {
>> ..
>> }
>>
>> class MyStreamImpl : IStreamAssemblyA
>> {
>> .........
>> }
>>
>> IntPtr GetStreamImpl()
>> {
>> MyStreamImpl obj = new MyStreamImpl();
>> IntPtr ret =
>> Marshal.GetComInterfaceForObject(obj,typeof(IStreamAssemblyA));
>> return ret;
>> }
>> ///////////////////
>>
>>
>> Assembly B
>> Gets and uses a COM IStream interface from the unmanaged world. In
>> case the implementation is an unmanaged one, everything works OK. In
>> case the implementation is actually from assembly A above (or any
>> other managed implementation), the cast fails as shown below.....
>> ==========
>>
>> /////////////////
>> [ComImport]
>> [GUID("..")]
>> interface IStreamAssemblyB
>> {
>> ..
>> }
>>
>> IntPtr GetStreamFromUnmanagedWorld()
>> {
>> ..
>> }
>>
>> void UseStream()
>> {
>> IntPtr streamUnk = GetStreamFromUnmanagedWorld();
>>
>> object obj = Marshal.GetObjectForIUnknown(streamUnk); // obj is
>> actually class MyStreamImpl from assembly A above
>>
>> IStreamAssemblyB stream = obj as IStreamAssemblyB; // this fails
>> becuase of different ".Net type" of obj and stream
>> }
>> /////////////////
>>
>>
>> The above problem exists becuase .Net does not recognize that even though
>> IStreamAssemblyA and IStreamAssemblyB are different ".Net types" they are
>> actually COM interfaces imported into .Net and so the cast above should
>> be
>> allowed (and QueryInterface should be used internally).
>>
>> How can I solve this issue? Its not possible to have a common IStream
>> declartion becuase AssemblyA and AssemblyB are not related in any way
>> except
>> to the extent that assembly B happens to use the managed IStream
>> implementation from assembly A.
>>
>> Any help would be appreciated!
>>
>> Bob
>