public static IEnumerable<T> TrimOrExpand<T>(this T[] items, int desiredCount)
{
    var ratio = (double)items.Length / desiredCount;
    for (int i = 0; i < desiredCount; i++)
        yield return items[Convert.ToInt32(i * ratio)];
}

public static IEnumerable<T> NormalizeObjects<T>(this T[] items, int desiredCount)

public static IEnumerable<T> ExpandOrContract<T>(this T[] items, int desiredCount)