Static Helper Class vs Static Method on an Instance Class vs Extension Method

Question

I'm looking for a best practice approach to the following problem.

I'd like peoples opinion's on which method(s) they would use, and why, to the following scenario:

I've got a Class which is instantiated by a factory when a DateTime is specified.

Which approach should I use?

static "helper" class : Class c = ClassHelper.GetClass(DateTime);
static method on the instance type : Class c = Class.GetClass(DateTime);
static extension class/method : Class c = DateTime.GetClass();

Currently I'm leaning more towards the static helper class as I've never taken the approach of having static factory methods on an instance class before, but it seems to make sense for me to do it with a static method on the class?

Are there any considerations I should be making when it comes to unit testing or organising tests?

I've steered clear of extension methods at the moment as I read that extension methods should be used sparingly, usually if you don't have access to the source you're extending?

Cheers,

James

Answer 1

I've got a Class which is instantiated by a factory when a DateTime is specified. Which approach should I use?

1. static "helper" class : Class c = ClassHelper.GetClass(DateTime);
2. static method on the instance type : Class c = Class.GetClass(DateTime);
3. static extension class/method : Class c = DateTime.GetClass();

My recommendation is to follow the principle of the simplest thing that could possibly work and code cohesion.

This means avoid extensions and helper classes, and just put the factory function in the Class class definition. Besides this is where people usually put factory functions.