Re: http://d.hatena.ne.jp/okazuki/20110609/1307577527

gistfile1.cs

using System.Linq;
using System.Text;
using System.Diagnostics;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var array = new[] { "1", "aaa", "2", "bbb", "1", "ccc", "4" };
            foreach (var i in array.ZipNext().ToDictionary())
            {
                Debug.WriteLine(i);
            }
        }
    }

    static class Ex
    {
        public static IEnumerable<Tuple<T, T>> ZipNext<T>(this IEnumerable<T> source)
        {
            using (var e = source.GetEnumerator())
            {
                while (e.MoveNext())
                {
                    var item = e.Current;
                    if (e.MoveNext())
                    {
                        yield return Tuple.Create(item, e.Current);
                    }
                }
            }
        }
        public static Dictionary<T, T> ToDictionary<T>(this IEnumerable<Tuple<T, T>> source)
        {
            return source.ToLookup(t => t.Item1).ToDictionary(g => g.Key, g => g.Last().Item2);
        }
    }
}