Populating a list of integers in .NET

Question

I need a list of integers from 1 to x where x is set by the user. I could build it with a for loop eg assuming x is an integer set previously:

List

        

Answer 1

Here is a short method that returns a List of integers.

    public static List<int> MakeSequence(int startingValue, int sequenceLength)
    {
        return Enumerable.Range(startingValue, sequenceLength).ToList<int>();
    }

Answer 2

I'm one of many who has blogged about a ruby-esque To extension method that you can write if you're using C#3.0:

public static class IntegerExtensions
{
    public static IEnumerable<int> To(this int first, int last)
    {
        for (int i = first; i <= last; i++)

        { 
            yield return i;
        } 
    }
}

Then you can create your list of integers like this

List<int> = first.To(last).ToList();

or

List<int> = 1.To(x).ToList();

Answer 3

LINQ to the rescue:

// Adding value to existing list
var list = new List<int>();
list.AddRange(Enumerable.Range(1, x));

// Creating new list
var list = Enumerable.Range(1, x).ToList();

See Generation Operators on LINQ 101

Answer 4

If you're using .Net 3.5, Enumerable.Range is what you need.

Generates a sequence of integral numbers within a specified range.