Why is the ForEach method only for lists

Question

From what I can see, the ForEach method is available only for the List class.

Why is that? I can see no reason for ForEach not to be available to any class implementing the IEnumerable/IEnumerator interfaces, and this is a really useful method if you need to perform a small action (1 line is more readable than 1 line + 2 boilerplate foreach syntax...).

Update: I'll clarify my question. There are perfectly valid reasons for including ForEach in sequences. There are perfectly good reasons for not including ForEachin all sequences.

But I cannot understand why would ForEach be included in just some of the sequences.

Answer 1

See Eric Lippert's post: "foreach" vs "ForEach"

A number of people have asked me why there is no Microsoft-provided “ForEach” sequence operator extension method. The List class has such a method already of course, but there’s no reason why such a method could not be created as an extension method for all sequences.

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But we can go a bit deeper here. I am philosophically opposed to providing such a method, for two reasons.

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The first reason is that doing so violates the functional programming principles that all the other sequence operators are based upon. Clearly the sole purpose of a call to this method is to cause side effects.

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The second reason is that doing so adds zero new representational power to the language.

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Well, the VS Languages team does not have any influence on what goes into List. I personally find the "ForEach" method on List philosophically troubling for all the same reasons that I would find an extension method on IEnumerable troubling. (And the VSL team does control that.) The one mitigating factor is that List is clearly designed to be a mutable, not-side-effect-free data structure, so using expressions that mutate it seems slightly less bad. -- Eric