using System;
using System.Globalization;
using System.Linq;
using System.Collections;
using System.Collections.Generic;

public class Test
{
	public static void Main()
	{
        int[] numbers = {1,2,2,3,3,4,4,5};
		var allUniques = numbers.GroupBy(i => i)
		    .Where(group => !group.CountMoreThan(1))
		    .Select(group => group.Key).ToList();
        foreach(int i in allUniques)
            Console.WriteLine(i);
	}
}

public static class Extensions
{
	public static bool CountMoreThan<TSource>(this IEnumerable<TSource> source, int num)
	{
	    if (source == null)
	        throw new ArgumentNullException("source");
	    if (num < 0)
	        throw new ArgumentException("num must be grater or equal 0", "num");
	
	    ICollection<TSource> collection = source as ICollection<TSource>;
	    if (collection != null)
	    {
	        return collection.Count > num;
	    }
	    ICollection collection2 = source as ICollection;
	    if (collection2 != null)
	    {
	        return collection2.Count > num;
	    }
	
	    int count = 0;
	    using (IEnumerator<TSource> enumerator = source.GetEnumerator())
	    {
	        while (++count <= num + 1)
	            if (!enumerator.MoveNext())
	                return false;
	    }
	    return true;
	}	
}