using System;

using System.Collections.Generic;

​

public class Program

{

    // Cache item

    public class DataControllerCacheItem  

    {

        protected DateTime _timeStamp;

        protected object   _item;

        public DataControllerCacheItem(object item) 

        {

            _timeStamp = DateTime.Now;

            _item = item;

        }   

        public TimeSpan age 

        {

            get { return DateTime.Now - _timeStamp; }

        }

        public object item

        {

            get { return _item; }

        }

    }

    public class DataControllerCache 

    {

        protected Dictionary<string, DataControllerCacheItem> _cache;

        public DataControllerCache()

        {

            _cache = new Dictionary<string, DataControllerCacheItem>();

        }

        public List<string> Sample 

        {

            get

            {

                return _get<List<string>>("Sample", () => new List<string>() { "pippo", "pluto", "paperino" });

            }

        }

        protected T _get<T>(string key, Func<T> generate)

        {

            T ret = default(T);

            bool found = false;

            lock(_cache) {

                DataControllerCacheItem data;

                if (_cache.TryGetValue(key, out data)) 

                {

                    if (data.age.TotalSeconds < 5)

                    {

                        ret = (T) data.item;

                        found = true;

                    }

                }

                if (!found) 

                {

                    ret = generate();

                    _cache.Add(key, new DataControllerCacheItem(ret));  

                }

            }           

            return ret;

        }

    }

    public static void Main()

    {

        var c = new DataControllerCache();

        var l = c.Sample;

        Console.WriteLine(l[0]);

        Console.WriteLine(l[1]);        

        Console.WriteLine("Hello World");

    }

}