linq - Why aren't C# static class extension methods supported?

Question

I know from this question that extension methods can only operate on class instances, not the static class itself. This means I can't extend useful static classes like Convert and Math.

What I want to know is, why is this the case? From the link above, there are some suggestions on how the C# team could have implemented this kind of functionality. Is there some philosophical reason why it isn't supported?

For example, here's a rationale behind why there is no built-in LINQ ForEach<T> extension for IEnumerable<T>.

Answer 1

the C# team could have implemented this kind of functionality. Is there some philosophical reason why it isn't supported?

There's no technical reason, and no philosophical reason. However, as I often point out, I don't have to provide a justification for not doing a feature. Features aren't cheap; they are extremely expensive and they must not only justify their own cost, they must justify the opportunity cost of not doing the hundred other features we could have done with that budget. We must justify the cost of features to our stakeholders, but we need not justify saving time and effort by not implementing features that don't meet our bar.

In particular, the proposed feature does nothing for LINQ; extension methods were added to make LINQ work. Anything that didn't make LINQ work was very hard to get into C# 3.0; we had a lot of work on the schedule and not much time to do it in. (I was surprised that automatic properties made it in.) Cutting an unnecessary feature before even designing it saved a lot of time and effort that was spent on other things that do make LINQ work.

In short: the suggested feature has never met our bar for net benefit over cost, and we've always had more important features to spend our limited time and effort on.