Question

I have a list like:

List<String> test = new List<String> {"Luke", "Leia"};

I would like to use something like this:

test.Select(s => String.Format("Hello {0}", s));

but it doesn’t adjust the names in the list. Is there a way to use lambda expressions to alter these? Or is it because strings are immutable that this doesn’t work?

Answer 1

Select doesn’t modify the original collection; it creates a new IEnumerable<T> that you can enumerate with a foreach or convert to a list:

List<String> test2 = test.Select(s => String.Format("Hello {0}", s)).ToList();

test still contains “Luke” and “Leia”, and test2 contains “Hello Luke” and “Hello Leia”.

---

If you want to modify the original list with a lambda expression, you can apply the lambda expression to each list item individually and store the result back in the collection:

Func<string, string> f = s => String.Format("Hello {0}", s);

for (int i = 0; i < test.Count; i++)
{
    test[i] = f(test[i]);
}