using System;

using System.Collections.Generic;

public class Program

{

    public class DataItem

    {

        public int ID { get; set; }

        public string Name { get; set; }

        public DataItem RefItem { get; set; }

    }    

​

    public class Checker

    {

        public static bool Check(DataItem item)

        {

            var chain = new Dictionary<DataItem, DataItem>();

            chain.Add(item, null);

            try

            {

                ProcessNodes(chain, item);

                return true;

            }

            catch (ArgumentException)

            {

                return false;

            }

        }

​

        private static void ProcessNodes(Dictionary<DataItem, DataItem> chain, DataItem item)

        {

            if (item.RefItem != null)

            {                

                chain.Add(item.RefItem, null);

                ProcessNodes(chain, item.RefItem);

            }

        }

        public static bool ValidateDataItems(List<DataItem> items)

        {

            foreach(var item in items)

                if(!Check(item))

                    return false;

            return true;                

        }

    }

​

​

    public static void Main()

    {

        var item1 = new DataItem() { ID = 1, Name = "First Item", RefItem = null };

        var item2 = new DataItem() { ID = 1, Name = "First Item", RefItem = item1 };

        var item3 = new DataItem() { ID = 1, Name = "First Item", RefItem = item2 };

        item1.RefItem = item3;

​

        Console.WriteLine(Checker.Check(item1));

        item1.RefItem = null;

        Console.WriteLine(Checker.Check(item1));

​

        //Sample how to check all existing items    

        Console.WriteLine(Checker.ValidateDataItems(new List<DataItem>{item1, item2, item3}) ? "items is OK" : "One or more items have dependency");        

    }

}