>Adding an extension method ( say AddCollection) is a bad idea since it accepts an argument of IEnumerable(T).
>
>using items.Count() is slow - I guess it uses a foreach loop to count
>
>

>// don't do this at home
>
>public static void AddCollection<T>(this List<T> list, IEnumerable<T> items)
>		{
>
>			if (items.Count() <= Tuning.AddRangeMinimumItems) // 128
>			{
>				foreach (T item in items)
>					list.Add(item);
>			}
>			else
>			{
>				list.AddRange(items);
>			}
>		}
>

>
>An extension method that takes a whole array is a better idea - since array.Length is faster

And probably I wouldn't use such an extesnion when it already exists (Concat):

       static void UseConcat()
        {
            int[] buf = new int[Size];
            List<int> list = new List<int>();
            for (int i = nTimes; --i != 0; )
            {
                list.Concat(buf);
                list.Clear();
            }
       }

Cetin