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.NET Forum / .NET Framework / Interop / March 2007Marshal.GetTypedObjectForIUnknown and reference counts
Hello, Say I have an interface from IUnknown::QueryInterface that I want available in my .Net program. When QueryInterface returns, I am responsible for Release()ing it, but depending on whether GetTypedObjcetForIUnknown has already wrapped that object, it may or may not increase the reference count on the COM object. How do I know when to Release()? Per the MSDN documentation, the object returned is a runtime callable wrapper. The runtime callable wrapper maintains and releases the interface pointers. See: http://msdn2.microsoft.com/en-us/library/8bwh56xe.aspx > Hello, > [quoted text clipped - 4 lines] > not increase the reference count on the COM object. How do I know when to > Release()? Yes, I realise that. But consider this: - IUnknown::QueryInterface returns an IntPtr to an interface. The reference count is 1. - GetTypedObjectForIUnknown is called to generate a RCW. It generates a new RCW, now the reference count is 2. - I use Marshal.ReleaseComObject to release the original reference. That's all fine. We have 1 reference to the interface, that of the RCW. Now consider this situation. - IUnknown::QueryInterface returns an IntPtr to an interface. The reference count is N. - GetTypedObjectForIUnknown is called to generate a RCW. It has already generated a RCW for this object in the past so the reference count is unchanged. - I use Marshal.ReleaseComObject to release the original reference. This decreases the count back to N-1, prematurely freeing the object. Am I misunderstanding something fundamental here? Regards Steve > Per the MSDN documentation, the object returned is a runtime callable > wrapper. [quoted text clipped - 11 lines] >> not increase the reference count on the COM object. How do I know when to >> Release()? COM rules always apply. For unmanaged COM objects, you are responsible for the reference count bookeeping per the COM guidelines. For managed COM objects that use the RCW mechanism, the RCW handles the reference count bookeeping per the COM guidelines. > Yes, I realise that. But consider this: > [quoted text clipped - 35 lines] >>> not increase the reference count on the COM object. How do I know when >>> to Release()?
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