[Why is it better to see it?] The problem with the com contract

[From essential. Net]
COM specification does not have a contract definitions.
Microsoft defined and supported two formats for com contract Description: Interface Definition Language (IDL) and Type Library (TLB), and these two formats are not in equivalence and also not subset of each other.
Seems worse, com contract does not include component dependencies information. you won't know a specifical DLL needs what other DLLs to make it work. also, you won't be able to know the required version of the needed DLL. seeing this, I feel that. net is really cool and mature, these pain all goes away in. net.
And the last one mentioned in the chapter is that com contract lack of extensibility, an example is when working with the Microsoft Transaction Server (MTS) (designed based on the idea of Aspect-oriented programming (AOP), developers must insert the declarative attributes, but this is only available to C ++ er, VB and maybe other extensions ages hide the IDL from the programmer, so it limites this AOP based idea only in the C ++. it's a totally different story in. net.