InterfaceTypeAttribute

InterfaceTypeAttribute is a .NET attribute used to specify the interface type that a class or struct implements. It is primarily used in conjunction with the COM interop features of the .NET Framework to define how a managed type is exposed to COM clients.

When a class or struct is marked with InterfaceTypeAttribute, the attribute's value indicates the specific COM interface invocation mechanism to be used. The attribute takes one of the values from the ComInterfaceType enumeration: InterfaceIsDual, InterfaceIsIUnknown, or InterfaceIsIDispatch.

InterfaceIsDual is used when the interface supports both early binding (through vtables) and late binding (through IDispatch). InterfaceIsIUnknown is used when the interface is not dual and is accessed solely through IUnknown. InterfaceIsIDispatch is used when the interface is dispatch-only and can only be accessed through IDispatch, typically for scripting scenarios.

This attribute is important for controlling how COM clients interact with .NET objects, ensuring correct method resolution and type information exchange. It is applied at the class or struct level and is typically used when exposing .NET types as COM components. The attribute helps bridge the gap between the .NET type system and the COM type system, facilitating interoperability.