Auto-Initializing C# Lists

Question

I am creating a new C# List (List<double>). Is there any way, other than to do a loop over the list, to initialize all the starting values to 0? Thank you.

Answer 1

well, you can use the initializer

var listInt = new List<int> {4, 5, 6, 7};
var listString = new List<string> {"string1", "hello", "world"};
var listCustomObjects = new List<Animal> {new Cat(), new Dog(), new Horse()};

Edited to fit the question.

So you could be using this

var listInt = new List<double> {0.0, 0.0, 0.0, 0.0};

Otherwise, using the default constructor, the List will be empty.

Answer 2

If you create a new list of int, the starting values of all elements will be zero anyway. No code required.

Answer 3

Enumerable.Repeat(0d, 25).ToList();
new List<double>(new double[25]);     //Array elements default to 0

EDIT: Changed int to double to match the question

2^nd EDIT: Fixed first call

Answer 4

For more complex types:

List<Customer> listOfCustomers =
        new List<Customer> {
            { Id = 1, Name="Dave", City="Sarasota" },
            { Id = 2, Name="John", City="Tampa" },
            { Id = 3, Name="Abe", City="Miami" }
        };

from here: David Hayden's Blog

Answer 5

One possibility is to use Enumerable.Range:

int capacity;
var list = Enumerable.Range(0, capacity).Select(i => 0d).ToList();

Another is:

int capacity;
var list = new List<double>(new double[capacity]);

Answer 6

In addition to the functional solutions provided (using the static methods on the Enumerable class), you can pass an array of doubles in the constructor.

var tenDoubles = new List<double>(new double[10]);

This works because the default value of an double is already 0, and probably performs slightly better.