StaticCachedList.cs

public class CachedLocationService : LocationService
    {
        private static List<StoreLocation> locations;
        private static DateTime expireTime = DateTime.UtcNow;
        private static object syncLock = new object();

        public CachedLocationService(DataModelContainer dataModelContainer)
            : base(dataModelContainer) { }

        public override StoreLocation GetByStoreNumber(int storeNumber)
        {
            return this.GetAll().Single(s => s.StoreNumber == storeNumber);
        }

        public override List<StoreLocation> GetAll()
        {
            if (locations == null)
            {
                UpdateCache();
                if (locations == null)
                {
                    throw new InvalidOperationException("There was an error loading the store locations from the database. The cache is currently null.");
                }
            }
            else
            {
                var task = new Task(() => { UpdateCache(); });
                task.Start();
            }
            return locations.ToList();
        }

        public override List<StoreLocation> GetByPosition(Position position, int numberToReturn = 10, double distanceLimit = 50)
        {
            return LocationService.GetByPosition(position, numberToReturn, distanceLimit, this.GetAll());
        }

        private void UpdateCache()
        {
            if (DateTime.UtcNow >= expireTime)
            {
                lock (syncLock)
                {
                    if (DateTime.UtcNow >= expireTime)
                    {
                        List<StoreLocation> newLocations = null;
                        try
                        {
                            newLocations = base.GetAll();
                        }
                        catch
                        {
                            newLocations = null;
                        }
                        if (newLocations != null)
                        {
                            locations = newLocations;
                            expireTime = DateTime.UtcNow.AddHours(1);
                        }
                    }
                }
            }
        }
    }