>>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
>
>Gregory,
>Sorry I didn't read the whole thread to see your purpose and solutions so far, could you use and try Linq Concat()? ie:
>

>	public static void AddCollection<T>(this List<T> list, IEnumerable<T> items)
>	{
>			list.Concat( items );
>	}
>

>
>Update: I made a short test with this using your original test and probably I am doing something wrong, results are unbelievably fast:
>
>00:00:05.5402003 // UseAddRange
>00:00:01.9798588 // UseForeach
>00:00:00.3055594 // UseConcat
>
>Thinking F# power and sequence processing behind Linq that result might be perfectly right. Here is my UseConcat BTW:
>
>

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

>Cetin

Cetin,

I started testing and wow concat is very fast.
Alas. It just returns another Enumerator which plugs the two enumerators together

Return Value
Type: System.Collections.Generic..::.IEnumerable <(Of <(TSource>)>)
An IEnumerable<(Of <(T>)>) that contains the concatenated elements of the two input sequences.

This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

It's easily seen in the debugger

			int[] pp = new int[Size];

			List<int> list = new List<int>();

			var tt = list.Concat(pp);

		i	0	int
+		pp	{int[256]}	int[]
+		list	Count = 0	System.Collections.Generic.List<int>
-		tt	{System.Linq.Enumerable.ConcatIterator<int>}	System.Collections.Generic.IEnumerable<int> {System.Linq.Enumerable.ConcatIterator<int>}
		first	null	System.Collections.Generic.IEnumerable<int>
		second	null	System.Collections.Generic.IEnumerable<int>
+		Non-Public members		
+		Results View	Expanding the Results View will enumerate the IEnumerable	

It's the about the same as my Queue.Reverse() - remember ?

Thanks,