分享一个单例模型类Singleton代码

相关代码：

using System;
using System.Collections.Generic;
using System.Text;

namespace Pixysoft.DesignPattern
{
    public class Singleton<T>
    {
        private Dictionary<string, T> dict = new Dictionary<string, T>();

        private string _id = null;

        private static volatile object instance;

        private static object syncRoot = new Object();

        public static T Instance
        {
            get
            {
                if (instance == null)
                {
                    lock (syncRoot)
                    {
                        instance = Activator.CreateInstance(typeof(T));
                    }
                }

                return (T)instance;

            }
        }

        public T this[string id]
        {
            get
            {
                //如果是null，表示自己，则直接返回Instance

                if (string.IsNullOrEmpty(id))
                    return Instance;

                id = id.Trim().ToUpper();

                lock (syncRoot)
                {
                    if (dict.ContainsKey(id))
                        return dict[id];

                    object i = Activator.CreateInstance(typeof(T));

                    ((Singleton<T>)i)._id = id;

                    T it = (T)i;

                    dict.Add(id, it);

                    return it;
                }
            }
        }

        public T this[int index]
        {
            get
            {
                if (index < 0 || index > dict.Keys.Count - 1)
                    return Instance;

                int coutner = 0;

                foreach (string key in dict.Keys)
                {
                    if (coutner >= index)
                        return dict[key];

                    coutner++;
                }

                return Instance;

            }
        }

        public string SingletonId
        {
            get { return _id; }
        }
    }
}

使用方法：

    class testclass
    {
        private void test()
        {
            Hello.Instance.Test();

            Hello.Instance["id"].Test();
        }
    }

    public class Hello : Singleton<Hello>
    {

        public void Test()
        {
            Console.Write("hello");
        }
    }

看看有什么错误等，希望能够指出。