Question

From what I have read about extension methods, you will run into problems if the base class decides to add a method with the same name as your extension. For a specific class it is generally not to hard to pick a name to avoid clashes, however extension methods can be added to interfaces which adds infinitely more potential for conflicts.

In Objective-C (with their version, categories), this problem is avoided by adding a prefix before each method. I know we can define extension methods in namespaces so that we can control whether they are imported or not, but this only solves the problem of clashes between extension methods, rather than clashes between an extension method and the base class.

Update:

Nobody, actually mentioned this, but extension methods aren’t virtual. That means if you can i.myExtension() on an interface i, then it will always call the interface classes method, so the subclass method (which could have different intent) won’t be called. So, overall, using extension methods is quite safe.

Answer 1

The use of a prefix will make the code ugly, which removes some of the value of an extension method.

I recommend instead, being careful to not create a large number of extension methods and to use method names that make sense. This way, in the case of a conflict, it’s more likely that, for instance, the extension Where method and the conflicting Where method will have similar semantics.