Performance IEnumerable.ToList().ForEach() over loop

Question

Is there any performance difference between these two statements?

IEnumerable<T>.ToList().ForEach(x => Console.WriteLine(x));

and

foreach (var obj in IEnumerable<T>)
   Console.WriteLine(obj)

You have a compiler and access to the `Stopwatch` class - why not test it yourself? — Oded, Apr 12 '13 at 10:04
Yes, because you don't have to create a List instance foreach over IEnumerable should be quicker. — MarcinJuraszek, Apr 12 '13 at 10:06
Arran, its not an duplicate because my object is a IEnumerable and I have to create a list first. — Martin Brandl, Apr 12 '13 at 10:07
Hence why it's a *possible* duplicate, if you don't agree, don't close it :) — Arran, Apr 12 '13 at 10:10
Hence my confirmation that it is definitely not a duplicate :) — Alex, Apr 12 '13 at 10:11
'Confirmation' is not required, confirmation is merely don't vote to close. — Arran, Apr 12 '13 at 10:11

score 4 · Accepted Answer · answered Apr 12 '13 at 10:07

In the first example, you will

Create a list by enumerating the source
Enumerate through the new list and call Console.WriteLine for each element.

In the second example, you will

There are two performance penalities to the first over the second:

1 Answers1