How can I use linq to initialize an array of repeated elements?

Question

At present, I'm using something like this to build a list of 10 objects:

myList = (from _ in Enumerable.Range(0, 10) select new MyObject {...}).toList()

This is based off my python background, where I'd write:

myList = [MyObject(...) for _ in range(10)]

Note that I want my list to contain 10 instances of my object, not the same instance 10 times.

Is this still a sensible way to do things in C#? Is there a cost to doing it this way over a simple for loop?

Answer 1

You can try:

Enumerable.Range(0, 1000).Select(x => new MyObject()).ToArray();

Answer 2

Fluent API looks a little more readable in this case, but its not very easy to see the intent of your code:

var list = Enumerable.Range(0, 10).Select(_ => new MyObject()).ToList();

Simple if loop is fast and easy to understand, but it also hides intent - creating list of 10 items

List<MyObject> list = new List<MyObject>();
for (int i = 0; i < 10; i++)
     list.Add(new MyObject());

The best thing for readability is a builder, which will describe your intent

public class Builder<T>
    where T : new()
{
    public static IList<T> CreateListOfSize(int size)
    {
        List<T> list = new List<T>();
        for (int i = 0; i < size; i++)
            list.Add(new T());
        return list;
    }
}

Usage:

var list = Builder<MyObject>.CreateListOfSize(10);

This solution is as fast, as simple loop, and intent is very clear. Also in this case we have minimum amount of code to write.