IUnknown interface -for COM \COM + objects?

Question

I am bit unclear in using IUnknown interface. Is IUnknown interface only meant to work with COM /COM + Objects and some unmanaged codes like Win APIs?

Answer 1

COM interfaces are used primarily by unmanaged code. If you need the C# you are writing to interoperate with unmanaged code, you can export it as COM interfaces:

COM Interop with C#

IUnknown is generally the base class for COM objects.

Answer 2

In context of C# and .NET - yes. You should use IUnknown only for COM.

Answer 3

IUnknown is a COM/COM+ interface. Its not used natively by .NET languages such as C#.