Fisher-Yates algorithm shuffle an array with O(n) time complexity

shuffle.cs

/// <summary>
/// Fisher-Yates algorithm with O(n) time complexity
/// </summary>
/// <param name="array">array to be shuffled</param>
/// <returns>shuffled array</returns>
public static int[] FisherYates(int[] array)
{
    Random r = new Random();
    for (int i = array.Length - 1; i > 0; i--)
    {
        int index = r.Next(i);

        // swap
        int tmp = array[index];
        array[index] = array[i];
        array[i] = tmp;
    }

    return array;
}