ASP.NET System.Web.Abstractions why were they created as an abstract Base class?

Question

As above really, I'm wondering why Microsoft released the abstractions as abstract classes instead of interfaces?

I would be interested in any insights because I need to do something similar for standard things like System.IO features for File and Directory, however I feel that an interface would feel nicer?

There must be a good reason why an abstract was chosen instead, other than the fact it fits into their assembly namespace better, System.Web.ABSTRACTions.

Thanks

Answer 1

I believe Phil (Haack, from the ASP.NET MVC team) explained this decision on his blog. Check out this post:

Versioning Issues With Abstract Base Classes and Interfaces