COM DCOM Question:

What is IUnknown? What methods are provided by IUnknown?

COM DCOM Interview Question
COM DCOM Interview Question

Answer:

IUnknown is a type of COM Interface.

Every COM class implements an interface named IUnKnown.

IUnKnown contains three methods:
1) HRESULT QueryInterface()
2) ULONG AddRef()
3) ULONG Release()


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What are the purposes of AddRef, Release and QueryInterface functions?What should QueryInterface functions do if requested object was not found?