using System;
using System.Collections.Generic;

namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            Random rnd = new Random(123);
            LinkedList<int> list = new LinkedList<int>();
            for (int i = 0; i < 25; i++)
            {
                list.AddLast(rnd.Next(0, 5));
            }
            Console.WriteLine("До:");
            foreach (var i in list)
            {
                Console.WriteLine(i);
            }
            Console.WriteLine();
            LinkedListNode<int> node;
            var d = 0;
            do
            {
                d = 0;
                node = list.First;
                while (node != null)
                {
                    int prev = -9999;
                    int next = -99;
                    if (node.Previous != null)
                    {
                        prev = node.Previous.Value;
                    }
                    if (node.Next != null)
                    {
                        next = node.Next.Value;
                    }
                    var nextNode = node.Next;
                    if (node.Value == prev || prev == next || node.Value == next)
                    {
                        d++;
                        Console.WriteLine("DELETE: Prev:{0} ,Curr:{1}, Next:{2}", prev, node.Value, next);
                        //Удаление элемента
                        list.Remove(node);
                    }
                    node = nextNode;
                }
            }
            while (d != 0);

            Console.WriteLine();

            Console.WriteLine("После:");

            foreach (var i in list)
            {
                Console.WriteLine(i);
            }
            Console.ReadKey();
        }
    }
}