Why there is no ForEach extension method on IEnumerable?


Question

Inspired by another question asking about the missing Zip function:

Why is there no ForEach extension method in the Enumerable class? Or anywhere? The only class that gets a ForEach method is List<>. Is there a reason why it's missing (performance)?

1
355
8/25/2015 9:44:15 AM

Accepted Answer

There is already a foreach statement included in the language that does the job most of the time.

I'd hate to see the following:

list.ForEach( item =>
{
    item.DoSomething();
} );

Instead of:

foreach(Item item in list)
{
     item.DoSomething();
}

The latter is clearer and easier to read in most situation, although maybe a bit longer to type.

However, I must admit I changed my stance on that issue; a ForEach() extension method would indeed be useful in some situations.

Here are the major differences between the statement and the method:

  • Type checking: foreach is done at runtime, ForEach() is at compile time (Big Plus!)
  • The syntax to call a delegate is indeed much simpler: objects.ForEach(DoSomething);
  • ForEach() could be chained: although evilness/usefulness of such a feature is open to discussion.

Those are all great points made by many people here and I can see why people are missing the function. I wouldn't mind Microsoft adding a standard ForEach method in the next framework iteration.

186
9/4/2012 1:41:54 PM

ForEach method was added before LINQ. If you add ForEach extension, it will never be called for List instances because of extension methods constraints. I think the reason it was not added is to not interference with existing one.

However, if you really miss this little nice function, you can roll out your own version

public static void ForEach<T>(
    this IEnumerable<T> source,
    Action<T> action)
{
    foreach (T element in source) 
        action(element);
}

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