Auto-initializing C# lists

user_132528 0
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I am creating a new C# List (List<double>). Is there a way, other than to do a loop over the list, to initialize all the starting values to 0?

list collections .net c#
6 Answers

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.

Walking_Disaster_76430

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()};

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.

user_768320

Use this code:

Enumerable.Repeat(0d, 25).ToList();
new List<double>(new double[25]);     //Array elements default to 0
user_343970

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]);
Jason_459140

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

user_1196600
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