Linq - lookahead Iteration

I am iterating thru a collection using a visitor-type pattern and need to access the current and next item in the list. At the moment I am doing it via an extension method like this

public void Visit<TItem>(this IEnumerable<TItem> theList, Action<TItem, TItem> visitor)
{
    for (i = 0; i <= theList.Count - 1; i++) {
        if (i == theList.Count - 1) {
            visitor(theList(i), null);
        } else {
            visitor(theList(i), theList(i + 1));
        }    
    }    
}

I was wondering whether there are other/better/more elegant ways to achieve this? At the moment I think I only need to have access to the current and next items in the list, but I'm wondering whether I may encounter situations where I may need to lookahead the next 'n' items, for example.