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For example, i have array of int and i need increase each element by 2. In modern c# with linq and extension methods the obvious solution is:

var array = new[] {1, 2, 3}; array.ForEach(p => p += 2);

But unfortunately, code will not compile, because ForEach is not extension method of IEnumerable, but its a member if List. So i need to use classic foreach loop or cast array to list, but this solutions not so elegant and simple.

Can anybody tell me, why Microsoft design ForEach method as member of List, but not as extension method of IEnumerable?

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    blogs.msdn.com/b/ericlippert/archive/2009/05/18/… Commented Aug 10, 2015 at 9:28
  • Your own sample is a great example of why in fact - you're causing horrible side effects, and it wouldn't work anyway (you're updating an argument, no the value in the array). LINQ is based on some functional paradigms, and one of the biggies is that you must not cause side-effects - if your code actually worked, that would be exactly what you'd be doing. The proper functional way would be to simply return a new array, of course - exactly what Select does. Not to mention that IEnumerable is a read-only contract - you're not going to modify it anyway. Commented Aug 10, 2015 at 9:43
  • @luaan Yes, you are right. Its bad example and bad idea to modify ValueTypes like this :) Commented Aug 10, 2015 at 9:45
  • @Luaan - The Ix-Main NuGet package from the Reactive Extensions team provides a ForEach extension method for IEnumerable. So it would seem that somebody at Microsoft finds value in it. Commented Aug 10, 2015 at 14:25
  • @JasonBoyd That quite agrees with Eric's point. In any case, there's plenty of things everyone at Microsoft doesn't agree on :) Reactive Extensions' ForEach is quite explicitly for side-effects - it's handy when using Rx for scheduling, for example (something like Observable.Interval(TimeSpan.FromSeconds(1)).Take(5).ForEach(i => Console.WriteLine(i))). It also stands in contrast to Subscribe. It's adding a bit of TPL into Rx in a way. Commented Aug 10, 2015 at 15:36
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