Getting random numbers from a list of integers

Question

If I have a list of integers:

List myValues = new List(new int[] { 1, 2, 3, 4, 5, 6 } );

How would I get 3 random integer

Answer 1

The simplest way would be something like this:

var r = new Random();
var myValues = new int[] { 1, 2, 3, 4, 5, 6 }; // Will work with array or list
var randomValues = Enumerable.Range(0, 3)
    .Select(e => myValues[r.Next(myValues.Length)]);

But a better method, if you want to ensure there are no duplicates is to use a shuffling algorithm, like the Fisher-Yates algorithm, then take the first 3 items:

public static T[] Shuffle(IEnumerable items)
{
    var result = items.ToArray();
    var r = new Random();
    for (int i = items.Length; i > 1; i--)
    {
        int j = r.Next(i);
        var t = result[j];
        result[j] = result[i - 1];
        result[i - 1] = t;
    }

    return result;
}

var myValues = new int[] { 1, 2, 3, 4, 5, 6 }; // Will work with any enumerable
var randomValues = myValues.Shuffle().Take(3);