Question

Now with

IList<string> listOfStrings = (new string[] {  "bob","mary"});

We can not preform

listOfStrings.ToList().ForEach(i => i.DoSome(i)));

We need to reshape to the concrete implementation of the Interface

List<string> listOfStrings = ((new string[] {  "bob","mary"}).ToLIst();

Then we can do a for each

listOfStrings.ForEach(i => i.DoSome(i)));

Is this because the foreach operator does not work with the IList Interface and why is this ??

Answer 1

You’re not using the foreach operator – you’re using a ForEach method, which is declared on List<T> (here) and also for arrays. There’s no such extension method on IList<T> or IEnumerable<T>. You could write one, but personally I’d use a real foreach loop:

foreach (var text in listOfStrings)
{
    ...
}

See Eric Lippert’s blog post on the topic for thoughts that are rather more lucid than mine.