Pagination Numbers (C#)

pagination.cs

// https://gist.github.com/kottenator/9d936eb3e4e3c3e02598
public static int[] Pagination(int current, int last)
{
    int delta = 2;
    int left = current - delta;
    int right = current + delta + 1;
    var range = new List<int>();
    var rangeWithDots = new List<int>();
    int? l = null;

    for (var i = 1; i <= last; i++)
    {
        if (i == 1 || i == last || i >= left && i < right)
        {
            range.Add(i);
        }
    }

    foreach (var i in range)
    {
        if (l != null)
        {
            if (i - l == 2)
            {
                rangeWithDots.Add(l.Value + 1);
            }
            else if (i - l != 1)
            {
                rangeWithDots.Add(-1);
            }
        }
        rangeWithDots.Add(i);
        l = i;
    }

    return rangeWithDots.ToArray();
}