Overriding Extension Methods

Question

I\'ve been thinking about using extension methods as a replacement for an abstract base class. The extension methods can provide default functionality, and can be \'overridd

Answer 1

First it would be good to check [new] as a method modifier - it should give the same perf and method separation but with a lot less of a hassle.

If after that you are are still pondering the same tricks, here are the principal options to consider - no ideology involved, just listing apsects you'll need to be aware of :-)

For a start you may have to limit all uses to templated function params in order to guarantee deterministic function selection since this trick will create the situation which is exact inverse of the one in which CLR guarantees deterministic binding priority across function call boundaries.

If you are still going to have abstract base class and you own all code then just "converting" one base method into extension weill not buy you anything at all and will just cost you the loss of a common interface which will still exist for everything else, including the cost of vtables.

If you are aiming at converting abstract class into a concrete, eliminating all virtual methods for perf reasons and using using concrete base class and all derivatives exclusively in templates (maybe even converting to structs) then that trick could buy you some perf. You just need to be aware that you won't be able to go back to interface-based use without refactoring. You'll also need to test invocation order in non-template functions with the base class in signature and be extra carefull if you have multiple dlls-s. Try the same with [new] operator and see if it works better.

Also, you will have to write separate method implementation for each derived class even if they have exactly the same functionality, so if you have a lot of derived classes you are looking at a lot of code duplication. This part will hit you even if you use [new] unless you go back to virtual methods and introduce another layer in inheritance - which will cancel all perf gains of course.