PIA (Primary Interop Assemblies)

What is a PIA? (主要互通組件)

Like any other managed assembly, an interop assembly is a collection of types that are deployed, versioned, and configured as a single unit. However, unlike other managed assemblies, an interop assembly contains type definitions (not implementation) of types that have already been defined in COM. These type definitions allow managed applications to bind to the COM types at compile time and provide information to the common language runtime about how the types should be marshaled at run time.

While any number of interop assemblies may exist that describe a given COM type, only one interop assembly is labeled the PIA. The PIA contains the official description of the types as defined by the publisher of those types. The PIA may contain certain customizations that make the types easier to use from managed code. The PIA is always signed by the publisher of the original COM type.

Any interop assembly that is not provided by the publisher of the COM types is considered unofficial and should be avoided. Because the types defined in such an assembly are not to be signed by the publisher of the PIA, they are incompatible with the definitions provided in the PIA.

有關 PIA 說明的文章，可參考
http://msdn.microsoft.com/en-us/library/aa302338.aspx