LazyInitializer.EnsureInitialized.cs

using System;
using System.Collections.Generic;

namespace Example.EnsureInitialized
{
    class Program
    {
        static void Main(string[] args)
        {
            var configurationService = new ConfigurationService();
            var configInfo = configurationService.ConfigInfo();

            foreach(var configItem in configInfo)
            {
                Console.WriteLine(configItem.Value);
            }

            Console.ReadKey();
        }
    }

    class ConfigurationService
    {
        private Dictionary<long, string> _simpleExample;

        public ConfigurationService()
        {
            System.Threading.LazyInitializer.EnsureInitialized(ref _simpleExample, Init);
        }

        private Dictionary<long, string> Init()
        {
            // The following would be replaced with some expensive operation like reading a file from disk.
            return new Dictionary<long, string>
            {
                {1, "Hello"},
                {2, "World"}
            };
        }

        public Dictionary<long, string> ConfigInfo()
        {
            return _simpleExample;
        }
    }
}