/// <summary>
        /// Converts a COM interface pointer to a managed object
        /// This either gets back a existing CCW, or a existing RCW, or create a new RCW
        /// </summary>
        internal static object ComInterfaceToObjectInternal(
            IntPtr pComItf,
            RuntimeTypeHandle interfaceType,
            RuntimeTypeHandle classTypeInSignature,
            CreateComObjectFlags flags)
        {
            bool needUnboxing = (flags & CreateComObjectFlags.SkipTypeResolutionAndUnboxing) == 0;

            object ret = ComInterfaceToObjectInternal_NoManagedUnboxing(pComItf, interfaceType, classTypeInSignature, flags);

            if (ret != null && needUnboxing)
            {
                return(UnboxManagedWrapperIfBoxed(ret));
            }

            return(ret);
        }
Exemplo n.º 2
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        /// <summary>
        /// Returns the existing RCW or create a new RCW from the COM interface pointer
        /// NOTE: Don't use this overload if you already have the identity IUnknown
        /// </summary>
        /// <param name="expectedContext">
        /// The current context of this thread. If it is passed and is not Default, we'll check whether the
        /// returned RCW from cache matches this expected context. If it is not a match (from a different
        /// context, and is not free threaded), we'll go ahead ignoring the cached entry, and create a new
        /// RCW instead - which will always end up in the current context
        /// We'll skip the check if current == ContextCookie.Default.
        /// </param>
        internal static object ComInterfaceToComObject(
            IntPtr pComItf,
            RuntimeTypeHandle interfaceType,
            RuntimeTypeHandle classTypeInSigature,
            ContextCookie expectedContext,
            CreateComObjectFlags flags
            )
        {
            Debug.Assert(expectedContext.IsDefault || expectedContext.IsCurrent);

            //
            // Get identity IUnknown for lookup
            //
            IntPtr pComIdentityIUnknown = McgMarshal.ComQueryInterfaceNoThrow(pComItf, ref Interop.COM.IID_IUnknown);

            if (pComIdentityIUnknown == default(IntPtr))
            {
                throw new InvalidCastException();
            }

            try
            {
                object obj = ComInterfaceToComObjectInternal(
                    pComItf,
                    pComIdentityIUnknown,
                    interfaceType,
                    classTypeInSigature,
                    expectedContext,
                    flags
                    );

                return(obj);
            }
            finally
            {
                McgMarshal.ComRelease(pComIdentityIUnknown);
            }
        }
Exemplo n.º 3
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        static object ComInterfaceToObjectInternal_NoManagedUnboxing(
            IntPtr pComItf,
            RuntimeTypeHandle interfaceType,
            RuntimeTypeHandle classTypeInSignature,
            CreateComObjectFlags flags)
        {
            if (pComItf == default(IntPtr))
                return null;

            //
            // Is this a CCW?
            //
            ComCallableObject ccw;

            if (ComCallableObject.TryGetCCW(pComItf, out ccw))
            {
                return ccw.TargetObject;
            }

            //
            // This pointer is not a CCW, but we need to do one additional check here for aggregation
            // In case the COM pointer is a interface implementation from native, but the outer object is a
            // managed object
            //
            IntPtr pComIdentityIUnknown = McgMarshal.ComQueryInterfaceNoThrow(pComItf, ref Interop.COM.IID_IUnknown);

            if (pComIdentityIUnknown == default(IntPtr))
                throw new InvalidCastException();

            try
            {
                //
                // Check whether the identity COM pointer to see if it is a aggregating CCW
                //
                if (ComCallableObject.TryGetCCW(pComIdentityIUnknown, out ccw))
                {
                    return ccw.TargetObject;
                }

                //
                // Nope, not a CCW - let's go down our RCW creation code path
                //
                return ComInterfaceToComObjectInternal(
                    pComItf,
                    pComIdentityIUnknown,
                    interfaceType,
                    classTypeInSignature,
                    ContextCookie.Default,
                    flags
                    );
            }
            finally
            {
                McgMarshal.ComRelease(pComIdentityIUnknown);
            }
        }
Exemplo n.º 4
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        /// <summary>
        /// Converts a COM interface pointer to a managed object
        /// This either gets back a existing CCW, or a existing RCW, or create a new RCW
        /// </summary>
        internal static object ComInterfaceToObjectInternal(
            IntPtr pComItf,
            RuntimeTypeHandle interfaceType,
            RuntimeTypeHandle classTypeInSignature,
            CreateComObjectFlags flags)
        {
            bool needUnboxing = (flags & CreateComObjectFlags.SkipTypeResolutionAndUnboxing) == 0;

            object ret = ComInterfaceToObjectInternal_NoManagedUnboxing(pComItf, interfaceType, classTypeInSignature, flags);
            if (ret != null && needUnboxing)
            {
                return UnboxManagedWrapperIfBoxed(ret);
            }

            return ret;
        }
Exemplo n.º 5
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        /// <summary>
        /// Returns the existing RCW or create a new RCW from the COM interface pointer
        /// NOTE: This does not do any unboxing at all. 
        /// </summary>
        /// <param name="expectedContext">
        /// The current context of this thread. If it is passed and is not Default, we'll check whether the
        /// returned RCW from cache matches this expected context. If it is not a match (from a different 
        /// context, and is not free threaded), we'll go ahead ignoring the cached entry, and create a new
        /// RCW instead - which will always end up in the current context
        /// We'll skip the check if current == ContextCookie.Default. 
        /// </param>
        private static object ComInterfaceToComObjectInternal_NoCache(
            IntPtr pComItf,
            IntPtr pComIdentityIUnknown,
            RuntimeTypeHandle interfaceType,
            RuntimeTypeHandle classTypeInSignature,
            ContextCookie expectedContext,
            CreateComObjectFlags flags,
            out string className
            )
        {
            className = null;

            //
            // Lookup RCW in global RCW cache based on the identity IUnknown
            //
            __ComObject comObject = ComObjectCache.Lookup(pComIdentityIUnknown);

            if (comObject != null)
            {
                bool useThisComObject = true;

                if (!expectedContext.IsDefault)
                {
                    //
                    // Make sure the returned RCW matches the context we specify (if any)
                    //
                    if (!comObject.IsFreeThreaded &&
                        !comObject.ContextCookie.Equals(expectedContext))
                    {
                        //
                        // This is a mismatch.
                        // We only care about context for WinRT factory RCWs (which is the only place we are
                        // passing in the context right now). 
                        // When we get back a WinRT factory RCW created in a different context. This means the
                        // factory is a singleton, and the returned IActivationFactory could be either one of 
                        // the following:
                        // 1) A raw pointer, and it acts like a free threaded object
                        // 2) A proxy that is used across different contexts. It might maintain a list of contexts
                        // that it is marshaled to, and will fail to be called if it is not marshaled to this 
                        // context yet.
                        //
                        // In this case, it is unsafe to use this RCW in this context and we should proceed
                        // to create a duplicated one instead. It might make sense to have a context-sensitive
                        // RCW cache but I don't think this case will be common enough to justify it
                        //
                        // @TODO: Check for DCOM proxy as well
                        useThisComObject = false;
                    }
                }

                if (useThisComObject)
                {
                    //
                    // We found one - AddRef and return
                    //
                    comObject.AddRef();
                    return comObject;
                }
            }

            string winrtClassName = null;

            bool isSealed = false;

            if (!classTypeInSignature.IsNull())
            {
                isSealed = classTypeInSignature.IsSealed();
            }

            //
            // Only look at runtime class name if the class type in signature is not sealed
            // NOTE: In the case of System.Uri, we are not pass the class type, only the interface
            //
            if (!isSealed &&
                (flags & CreateComObjectFlags.SkipTypeResolutionAndUnboxing) == 0)
            {
                IntPtr pInspectable;

                bool needRelease = false;

                if (interfaceType.IsSupportIInspectable())
                {
                    //
                    // Use the interface pointer as IInspectable as we know it is indeed a WinRT interface that
                    // derives from IInspectable
                    //
                    pInspectable = pComItf;
                }
                else if ((flags & CreateComObjectFlags.IsWinRTObject) != 0)
                {
                    //
                    // Otherwise, if someone tells us that this is a WinRT object, but we don't have a 
                    // IInspectable interface at hand, we'll QI for it
                    //
                    pInspectable = McgMarshal.ComQueryInterfaceNoThrow(pComItf, ref Interop.COM.IID_IInspectable);
                    needRelease = true;
                }
                else
                {
                    pInspectable = default(IntPtr);
                }

                try
                {
                    if (pInspectable != default(IntPtr))
                    {
                        className = McgComHelpers.GetRuntimeClassName(pInspectable);
                        winrtClassName = className;
                    }
                }
                finally
                {
                    if (needRelease && pInspectable != default(IntPtr))
                    {
                        McgMarshal.ComRelease(pInspectable);
                        pInspectable = default(IntPtr);
                    }
                }
            }

            //
            // 1. Prefer using the class returned from GetRuntimeClassName
            // 2. Otherwise use the class (if there) in the signature
            // 3. Out of options - create __ComObject
            //
            RuntimeTypeHandle classTypeToCreateRCW = default(RuntimeTypeHandle);
            RuntimeTypeHandle interfaceTypeFromName = default(RuntimeTypeHandle);

            if (!String.IsNullOrEmpty(className))
            {
                if (!McgModuleManager.TryGetClassTypeFromName(className, out classTypeToCreateRCW))
                {
                    //
                    // If we can't find the class name in our map, try interface as well
                    // Such as IVector<Int32>
                    // This apparently won't work if we haven't seen the interface type in MCG
                    //
                    McgModuleManager.TryGetInterfaceTypeFromName(className, out interfaceTypeFromName);
                }
            }

            if (classTypeToCreateRCW.IsNull())
                classTypeToCreateRCW = classTypeInSignature;

            // Use identity IUnknown to create the new RCW
            // @TODO: Transfer the ownership of ref count to the RCW
            if (classTypeToCreateRCW.IsNull())
            {
                //
                // Create a weakly typed RCW because we have no information about this particular RCW
                // @TODO - what if this RCW is not seen by MCG but actually exists in WinMD and therefore we
                // are missing GCPressure and ComMarshallingType information for this object?
                //
                comObject = new __ComObject(pComIdentityIUnknown, default(RuntimeTypeHandle));
            }
            else
            {
                //
                // Create a strongly typed RCW based on RuntimeTypeHandle
                //
                comObject = CreateComObjectInternal(classTypeToCreateRCW, pComIdentityIUnknown);            // Use identity IUnknown to create the new RCW
            }

#if DEBUG
            //
            // Remember the runtime class name for debugging purpose
            // This way you can tell what the class name is, even when we failed to create a strongly typed
            // RCW for it
            //
            comObject.m_runtimeClassName = className;
#endif

            //
            // Make sure we QI for that interface
            //
            if (!interfaceType.IsNull())
            {
                comObject.QueryInterface_NoAddRef_Internal(interfaceType, /* cacheOnly= */ false, /* throwOnQueryInterfaceFailure= */ false);
            }

            return comObject;
        }
Exemplo n.º 6
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        /// <summary>
        /// Returns the existing RCW or create a new RCW from the COM interface pointer
        /// NOTE: This does unboxing unless CreateComObjectFlags.SkipTypeResolutionAndUnboxing is specified
        /// </summary>
        /// <param name="expectedContext">
        /// The current context of this thread. If it is passed and is not Default, we'll check whether the
        /// returned RCW from cache matches this expected context. If it is not a match (from a different 
        /// context, and is not free threaded), we'll go ahead ignoring the cached entry, and create a new
        /// RCW instead - which will always end up in the current context
        /// We'll skip the check if current == ContextCookie.Default. 
        /// </param>
        internal static object ComInterfaceToComObjectInternal(
            IntPtr pComItf,
            IntPtr pComIdentityIUnknown,
            RuntimeTypeHandle interfaceType,
            RuntimeTypeHandle classTypeInSignature,
            ContextCookie expectedContext,
            CreateComObjectFlags flags
            )
        {
            string className;
            object obj = ComInterfaceToComObjectInternal_NoCache(
                pComItf,
                pComIdentityIUnknown,
                interfaceType,
                classTypeInSignature,
                expectedContext,
                flags,
                out className
                );

            //
            // The assumption here is that if the classInfoInSignature is null and interfaceTypeInfo
            // is either IUnknow and IInspectable we need to try unboxing.
            //
            bool doUnboxingCheck = 
                (flags & CreateComObjectFlags.SkipTypeResolutionAndUnboxing) == 0 &&
                obj != null &&
                classTypeInSignature.IsNull() && 
                (interfaceType.Equals(InternalTypes.IUnknown) ||
                 interfaceType.IsIInspectable());

            if (doUnboxingCheck)
            {
                //
                // Try unboxing
                // Even though this might just be a IUnknown * from the signature, we still attempt to unbox
                // if it implements IInspectable
                //
                // @TODO - We might need to optimize this by pre-checking the names to see if they 
                // potentially represents a boxed type, but for now let's keep it simple and I also don't
                // want to replicate the knowledge here
                // @TODO2- We probably should skip the creating the COM object in the first place.
                //
                // NOTE: the RCW here could be a cached one (for a brief time if GC doesn't kick in. as there
                // is nothing to hold the RCW alive for IReference<T> RCWs), so this could save us a RCW
                // creation cost potentially. Desktop CLR doesn't do this. But we also paying for unnecessary
                // cache management cost, and it is difficult to say which way is better without proper
                // measuring
                //
                object unboxedObj = McgMarshal.UnboxIfBoxed(obj, className);
                if (unboxedObj != null)
                    return unboxedObj;
            }

            //
            // In order for variance to work, we save the incoming interface pointer as specified in the 
            // signature into the cache, so that we know this RCW does support this interface and variance 
            // can take advantage of that later
            // NOTE: In some cases, native might pass a WinRT object as a 'compatible' interface, for example,
            // pass IVector<IFoo> as IVector<Object> because they are 'compatible', but QI for IVector<object>
            // won't succeed. In this case, we'll just believe it implements IVector<Object> as in the 
            // signature while the underlying interface pointer is actually IVector<IFoo>
            //
            __ComObject comObject = obj as __ComObject;

            if (comObject != null)
            {
                McgMarshal.ComAddRef(pComItf);

                try
                {
                    comObject.InsertIntoCache(interfaceType, ContextCookie.Current, ref pComItf, true);
                }
                finally
                {
                    //
                    // Only release when a exception is thrown or we didn't 'swallow' the ref count by
                    // inserting it into the cache
                    //
                    McgMarshal.ComSafeRelease(pComItf);
                }
            }

            return obj;
        }
Exemplo n.º 7
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        /// <summary>
        /// Returns the existing RCW or create a new RCW from the COM interface pointer
        /// NOTE: Don't use this overload if you already have the identity IUnknown
        /// </summary>
        /// <param name="expectedContext">
        /// The current context of this thread. If it is passed and is not Default, we'll check whether the
        /// returned RCW from cache matches this expected context. If it is not a match (from a different 
        /// context, and is not free threaded), we'll go ahead ignoring the cached entry, and create a new
        /// RCW instead - which will always end up in the current context
        /// We'll skip the check if current == ContextCookie.Default. 
        /// </param>
        internal static object ComInterfaceToComObject(
            IntPtr pComItf,
            RuntimeTypeHandle interfaceType,
            RuntimeTypeHandle classTypeInSigature,
            ContextCookie expectedContext,
            CreateComObjectFlags flags
            )
        {
            Debug.Assert(expectedContext.IsDefault || expectedContext.IsCurrent);

            //
            // Get identity IUnknown for lookup
            //
            IntPtr pComIdentityIUnknown = McgMarshal.ComQueryInterfaceNoThrow(pComItf, ref Interop.COM.IID_IUnknown);

            if (pComIdentityIUnknown == default(IntPtr))
                throw new InvalidCastException();

            try
            {
                object obj = ComInterfaceToComObjectInternal(
                    pComItf,
                    pComIdentityIUnknown,
                    interfaceType,
                    classTypeInSigature,
                    expectedContext,
                    flags
                    );

                return obj;
            }
            finally
            {
                McgMarshal.ComRelease(pComIdentityIUnknown);
            }
        }
Exemplo n.º 8
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        /// <summary>
        /// Returns the existing RCW or create a new RCW from the COM interface pointer
        /// NOTE: This does not do any unboxing at all.
        /// </summary>
        /// <param name="expectedContext">
        /// The current context of this thread. If it is passed and is not Default, we'll check whether the
        /// returned RCW from cache matches this expected context. If it is not a match (from a different
        /// context, and is not free threaded), we'll go ahead ignoring the cached entry, and create a new
        /// RCW instead - which will always end up in the current context
        /// We'll skip the check if current == ContextCookie.Default.
        /// </param>
        private static object ComInterfaceToComObjectInternal_NoCache(
            IntPtr pComItf,
            IntPtr pComIdentityIUnknown,
            RuntimeTypeHandle interfaceType,
            RuntimeTypeHandle classTypeInSignature,
            ContextCookie expectedContext,
            CreateComObjectFlags flags,
            out string className
            )
        {
            className = null;

            //
            // Lookup RCW in global RCW cache based on the identity IUnknown
            //
            __ComObject comObject = ComObjectCache.Lookup(pComIdentityIUnknown);

            if (comObject != null)
            {
                bool useThisComObject = true;

                if (!expectedContext.IsDefault)
                {
                    //
                    // Make sure the returned RCW matches the context we specify (if any)
                    //
                    if (!comObject.IsFreeThreaded &&
                        !comObject.ContextCookie.Equals(expectedContext))
                    {
                        //
                        // This is a mismatch.
                        // We only care about context for WinRT factory RCWs (which is the only place we are
                        // passing in the context right now).
                        // When we get back a WinRT factory RCW created in a different context. This means the
                        // factory is a singleton, and the returned IActivationFactory could be either one of
                        // the following:
                        // 1) A raw pointer, and it acts like a free threaded object
                        // 2) A proxy that is used across different contexts. It might maintain a list of contexts
                        // that it is marshaled to, and will fail to be called if it is not marshaled to this
                        // context yet.
                        //
                        // In this case, it is unsafe to use this RCW in this context and we should proceed
                        // to create a duplicated one instead. It might make sense to have a context-sensitive
                        // RCW cache but I don't think this case will be common enough to justify it
                        //
                        // @TODO: Check for DCOM proxy as well
                        useThisComObject = false;
                    }
                }

                if (useThisComObject)
                {
                    //
                    // We found one - AddRef and return
                    //
                    comObject.AddRef();
                    return(comObject);
                }
            }

            string winrtClassName = null;

            bool isSealed = false;

            if (!classTypeInSignature.IsNull())
            {
                isSealed = classTypeInSignature.IsSealed();
            }

            //
            // Only look at runtime class name if the class type in signature is not sealed
            // NOTE: In the case of System.Uri, we are not pass the class type, only the interface
            //
            if (!isSealed &&
                (flags & CreateComObjectFlags.SkipTypeResolutionAndUnboxing) == 0)
            {
                IntPtr pInspectable;

                bool needRelease = false;

                if (interfaceType.IsSupportIInspectable())
                {
                    //
                    // Use the interface pointer as IInspectable as we know it is indeed a WinRT interface that
                    // derives from IInspectable
                    //
                    pInspectable = pComItf;
                }
                else if ((flags & CreateComObjectFlags.IsWinRTObject) != 0)
                {
                    //
                    // Otherwise, if someone tells us that this is a WinRT object, but we don't have a
                    // IInspectable interface at hand, we'll QI for it
                    //
                    pInspectable = McgMarshal.ComQueryInterfaceNoThrow(pComItf, ref Interop.COM.IID_IInspectable);
                    needRelease  = true;
                }
                else
                {
                    pInspectable = default(IntPtr);
                }

                try
                {
                    if (pInspectable != default(IntPtr))
                    {
                        className      = McgComHelpers.GetRuntimeClassName(pInspectable);
                        winrtClassName = className;
                    }
                }
                finally
                {
                    if (needRelease && pInspectable != default(IntPtr))
                    {
                        McgMarshal.ComRelease(pInspectable);
                        pInspectable = default(IntPtr);
                    }
                }
            }

            //
            // 1. Prefer using the class returned from GetRuntimeClassName
            // 2. Otherwise use the class (if there) in the signature
            // 3. Out of options - create __ComObject
            //
            RuntimeTypeHandle classTypeToCreateRCW  = default(RuntimeTypeHandle);
            RuntimeTypeHandle interfaceTypeFromName = default(RuntimeTypeHandle);

            if (!String.IsNullOrEmpty(className))
            {
                if (!McgModuleManager.TryGetClassTypeFromName(className, out classTypeToCreateRCW))
                {
                    //
                    // If we can't find the class name in our map, try interface as well
                    // Such as IVector<Int32>
                    // This apparently won't work if we haven't seen the interface type in MCG
                    //
                    McgModuleManager.TryGetInterfaceTypeFromName(className, out interfaceTypeFromName);
                }
            }

            if (classTypeToCreateRCW.IsNull())
            {
                classTypeToCreateRCW = classTypeInSignature;
            }

            // Use identity IUnknown to create the new RCW
            // @TODO: Transfer the ownership of ref count to the RCW
            if (classTypeToCreateRCW.IsNull())
            {
                //
                // Create a weakly typed RCW because we have no information about this particular RCW
                // @TODO - what if this RCW is not seen by MCG but actually exists in WinMD and therefore we
                // are missing GCPressure and ComMarshallingType information for this object?
                //
                comObject = new __ComObject(pComIdentityIUnknown, default(RuntimeTypeHandle));
            }
            else
            {
                //
                // Create a strongly typed RCW based on RuntimeTypeHandle
                //
                comObject = CreateComObjectInternal(classTypeToCreateRCW, pComIdentityIUnknown);            // Use identity IUnknown to create the new RCW
            }

#if DEBUG
            //
            // Remember the runtime class name for debugging purpose
            // This way you can tell what the class name is, even when we failed to create a strongly typed
            // RCW for it
            //
            comObject.m_runtimeClassName = className;
#endif

            //
            // Make sure we QI for that interface
            //
            if (!interfaceType.IsNull())
            {
                comObject.QueryInterface_NoAddRef_Internal(interfaceType, /* cacheOnly= */ false, /* throwOnQueryInterfaceFailure= */ false);
            }

            return(comObject);
        }
Exemplo n.º 9
0
        /// <summary>
        /// Returns the existing RCW or create a new RCW from the COM interface pointer
        /// NOTE: This does unboxing unless CreateComObjectFlags.SkipTypeResolutionAndUnboxing is specified
        /// </summary>
        /// <param name="expectedContext">
        /// The current context of this thread. If it is passed and is not Default, we'll check whether the
        /// returned RCW from cache matches this expected context. If it is not a match (from a different
        /// context, and is not free threaded), we'll go ahead ignoring the cached entry, and create a new
        /// RCW instead - which will always end up in the current context
        /// We'll skip the check if current == ContextCookie.Default.
        /// </param>
        internal static object ComInterfaceToComObjectInternal(
            IntPtr pComItf,
            IntPtr pComIdentityIUnknown,
            RuntimeTypeHandle interfaceType,
            RuntimeTypeHandle classTypeInSignature,
            ContextCookie expectedContext,
            CreateComObjectFlags flags
            )
        {
            string className;
            object obj = ComInterfaceToComObjectInternal_NoCache(
                pComItf,
                pComIdentityIUnknown,
                interfaceType,
                classTypeInSignature,
                expectedContext,
                flags,
                out className
                );

            //
            // The assumption here is that if the classInfoInSignature is null and interfaceTypeInfo
            // is either IUnknow and IInspectable we need to try unboxing.
            //
            bool doUnboxingCheck =
                (flags & CreateComObjectFlags.SkipTypeResolutionAndUnboxing) == 0 &&
                obj != null &&
                classTypeInSignature.IsNull() &&
                (interfaceType.Equals(InternalTypes.IUnknown) ||
                 interfaceType.IsIInspectable());

            if (doUnboxingCheck)
            {
                //
                // Try unboxing
                // Even though this might just be a IUnknown * from the signature, we still attempt to unbox
                // if it implements IInspectable
                //
                // @TODO - We might need to optimize this by pre-checking the names to see if they
                // potentially represents a boxed type, but for now let's keep it simple and I also don't
                // want to replicate the knowledge here
                // @TODO2- We probably should skip the creating the COM object in the first place.
                //
                // NOTE: the RCW here could be a cached one (for a brief time if GC doesn't kick in. as there
                // is nothing to hold the RCW alive for IReference<T> RCWs), so this could save us a RCW
                // creation cost potentially. Desktop CLR doesn't do this. But we also paying for unnecessary
                // cache management cost, and it is difficult to say which way is better without proper
                // measuring
                //
                object unboxedObj = McgMarshal.UnboxIfBoxed(obj, className);
                if (unboxedObj != null)
                {
                    return(unboxedObj);
                }
            }

            //
            // In order for variance to work, we save the incoming interface pointer as specified in the
            // signature into the cache, so that we know this RCW does support this interface and variance
            // can take advantage of that later
            // NOTE: In some cases, native might pass a WinRT object as a 'compatible' interface, for example,
            // pass IVector<IFoo> as IVector<Object> because they are 'compatible', but QI for IVector<object>
            // won't succeed. In this case, we'll just believe it implements IVector<Object> as in the
            // signature while the underlying interface pointer is actually IVector<IFoo>
            //
            __ComObject comObject = obj as __ComObject;

            if (comObject != null)
            {
                McgMarshal.ComAddRef(pComItf);

                try
                {
                    comObject.InsertIntoCache(interfaceType, ContextCookie.Current, ref pComItf, true);
                }
                finally
                {
                    //
                    // Only release when a exception is thrown or we didn't 'swallow' the ref count by
                    // inserting it into the cache
                    //
                    McgMarshal.ComSafeRelease(pComItf);
                }
            }

            return(obj);
        }