A question I see from time-to-time on LINQ to SQL relates to changing an entity’s class.

C# and VB.NET don’t allow a class to change its type at run-time and LINQ to SQL specifically doesn’t provide a mechanism for changing the underlying discriminator for this reason.

I first encountered the Gang of Four Design Patterns book back in 2001 when a friend lent me a copy. I didn’t immediately get it, most likely because my object oriented experience up to that point consisted primarily of small Delphi applications.

In the last few years I’ve been working on much larger systems and have come to appreciate design patterns enough to get my own copy and also to invest in Martin Fowler’s excellent Patterns of Enterprise Architecture which provides higher-level patterns aimed at large data-driven applications.

While a big fan of patterns I found the original Gang of Four (GoF) book a little dry and so had left the pattern books alone until Martin Fowler’s Patterns of Enterprise Application Architecture (PEAA), got referenced so many times on-line I gave in and purchased a copy. I’m glad I did — even if the examples are mostly in Java with the very occasional one in C#.

The patterns in the original GoF were really about the interactions between the objects themselves and whilst PEAA has some object-to-object interactions it concentrates on problems encountered in “Enterprise Applications”. This includes database mappings, transactions, web pages and concurrency.