单例模式

 public class BaseSingleton
    {
        static BaseSingleton()
        {
            AllSingletons = new Dictionary<Type, object>();
        }

        /// <summary>
        /// Dictionary of type to singleton instances.
        /// </summary>
        public static IDictionary<Type, object> AllSingletons { get; set; }
    }

public class Singleton<T> : BaseSingleton
    {
        private static T instance;

        /// <summary>
        /// The singleton instance for the specified type T. Only one instance (at the time) of this object for each type of T.
        /// </summary>
        public static T Instance
        {
            get { return instance; }
            set
            {
                instance = value;
                AllSingletons[typeof(T)] = value;
            }
        }
    }

 public class QueueSingleton
    {
         public static WeiXinRechargeBLL Create()
         {
             //create NopEngine as engine
             return Singleton<WeiXinRechargeBLL>.Instance ?? (Singleton<WeiXinRechargeBLL>.Instance = new WeiXinRechargeBLL());
         }
    }