在密封類中實(shí)例化另一個(gè)類的推薦方法是什么：public sealed class AvayaService{    private static Lazy<AvayaService> lazy =       new Lazy<AvayaService>(() => new AvayaService());    public static AvayaService AvayaServiceInstance    {        get        {            if (!lazy.IsValueCreated)                lazy = new Lazy<AvayaService>(() => new AvayaService());            return lazy.Value;        }    }    private AvayaService()    {    }    public static Response GetResponse(Request request)    {       var _repository = new Repository(); //  what is the best way to get the instance here    }}public class Repository : IRepository{   ...}我正在嘗試學(xué)習(xí)密封類和惰性實(shí)例化，但是我正在思考在密封類中實(shí)例化另一個(gè)類的推薦方法是什么？