C# foreach loop with different action for final item

foreach-final-item.cs

public static class EnumerableExtensions
{
	/// <summary>
	/// Perform an action on each element of an IEnumerable<T>, optionally specifying a different action for the final item.
	/// </summary>
	public static void ForEach<T>(this IEnumerable<T> source, Action<T> action, Action<T> finalAction=null)
	{
		if (source == null)
		{
			throw new ArgumentNullException("source");
		}
		if (action == null)
		{
			throw new ArgumentNullException("action");
		}
		
		finalAction = finalAction ?? action;
	
		using(var iter = source.GetEnumerator())
		{
			if(iter.MoveNext())
			{
				T item = iter.Current;
				while(iter.MoveNext())
				{
					action(item);
					item = iter.Current;
				}
				finalAction(item);
			}
		}
	}
}