Fastest way to add a Range in a List C#

Question

I have to add about 3000 Elements to more than 20 Lists. The code that I am using:

LastChange = new List<string>();
LastChange.AddRange(Enumerable.Repeat("/", 3000));

same for more than 20 Lists...

Is there any "fastest way" to add "/" to the Lists or that is the best solution. Thanks in Advance...

`LastChange = new List(3000);` will be a little bit better: we allocate memory for `3000` items in order to avoid dynamic reallocation — Dmitry Bychenko, Nov 02 '21 at 08:27
@DmitryBychenko thanks. Could you please write the complete answer ?! — , Nov 02 '21 at 08:27
Why not [`LastChange = Enumerable.Repeat("/", 3000).ToList()`](https://stackoverflow.com/a/1120733/7831383)? I don't really get the point in using `AddRange` when your list isn't an existing list — Rafalon, Nov 02 '21 at 11:49

score 3 · Answer 1 · answered Nov 02 '21 at 08:32

A bit better solution is to allocate memory for 3000 items in the constructor in order to avoid memory reallocation:

 LastChange = new List<string>(3000);

 LastChange.AddRange(Enumerable.Repeat("/", 3000));

You can go further and get rid of IEnumerator<T> in Enumerable.Repeat:

 int count = 3000;

 LastChange = new List<string>(count);

 // compare to 0 is a bit faster then 3000
 for (int i = count - 1; i >= 0; --i)
   LastChange[i] = "\";

Fastest way to add a Range in a List C#

1 Answers1