In managed code, you seldom work directly with the IUnknown interface. However, Marshal.GetIUnknownForObject(object) is useful when calling a method that exposes a COM object parameter as an IntPtr type, or with custom marshaling. Calling an object with this method causes the reference count to increment on the interface pointer before the pointer is returned. Always use Marshal.Release(IntPtr) to decrement the reference count once you have finished with the pointer. This method provides the opposite functionality of the Marshal.GetObjectForIUnknown(IntPtr) method.

You can also use this method on a managed object to obtain an interface pointer to the COM Callable Wrapper for the object.

Namespace: System.Runtime.InteropServices
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0