c#没有synchronized？ 怎么实现单实例啊？

Question

给我写个简单的类
象征性的描述一下谢谢

Answer 1

        private static SocketUtil instance;
        private static readonly object syncRoot = new object();        public static SocketUtil getInstance()
        {
            lock (syncRoot)
            {
                if (instance == null)
                    instance = new SocketUtil();
            }
            return instance;
        }只有lock

Answer 2

没有private object m_mutex = new object();
private bool m_initialized = false;
private BigInstance m_instance = null;public BigInstance Instance
{
    get
    {
        if (!this.m_initialized)
        {
            lock (this.m_mutex)
            {
                if (!this.m_initialized)
                {
                    this.m_instance = new BigInstance();
                    this.m_initialized = true;
                }
            }
        }        return this.m_instance;
    }
}
直接上别人的代码