设计模式代码

单例模式1：

    /// <summary>
    /// 单例
    /// </summary>
    public sealed class Singleton
    {
        /// <summary>
        /// 锁
        /// </summary>
        private static object padlock = new object();

        /// <summary>
        /// 单例字段
        /// </summary>
        private static Singleton instance = null;

        /// <summary>
        /// 私有构造函数
        /// </summary>
        private Singleton()
        {
        }

        /// <summary>
        /// 实例
        /// </summary>
        public static Singleton Instance
        {
            get
            {
                if (instance == null)
                {
                    lock (padlock)
                    {
                        if (instance == null)
                        {
                            instance = new Singleton();
                        }
                    }
                }

                return instance;
            }
        }
    }

单例模式2：

 /// <summary>
    /// 单例
    /// </summary>
    public sealed class Singleton
    {
        /// <summary>
        /// 实例
        /// </summary>
        private static Singleton instance = new Singleton();

        /// <summary>
        /// 私有构造函数
        /// </summary>
        private Singleton()
        {
        }

        /// <summary>
        /// 实例
        /// </summary>
        public static Singleton Instance
        {
            get
            {
                return instance;
            }
        }
    }