public class CommonSigleton

    {

        /// <summary>

        /// 私有的对象

        /// </summary>

        private static CommonSigleton instance;

        /// <summary>

        /// 构造方法为Private

        /// </summary>

        private CommonSigleton()

        {

        }

        /// <summary>

        /// 公有的属性

        /// </summary>

        public static CommonSigleton Instance

        {

            get

            {

                if(instance == null)

                {

                    instance = new CommonSigleton();

                }

                return instance;

            }

        }

    }

    public class DoubLockSigleton

    {

        private static volatile DoubLockSigleton instance;

        /// <summary>

        /// 辅助锁对象，本身没有意义

        /// </summary>

        private static object syncRoot = new Object();

        /// <summary>

        /// 构造方法改为Private

        /// </summary>

        private DoubLockSigleton()

        {

        }

        public static DoubLockSigleton Instance

        {

            get

            {

                if (instance == null)

                {

                    lock (syncRoot)

                    {

                        if (instance == null)

                            instance = new DoubLockSigleton();

                    }

                }

                return instance;

            }

        }

    }

    ///该类标记sealed阻止发生派生增加实例

    public sealed class DotNetSigleton

    {

        //变量标记为 readonly，这意味着只能在静态初始化期间（此处显示的示例）或在类构造函数中分配变量。

        //公共静态属性为访问实例提供了一个全局访问点。此外，由于构造函数是私有的，因此不能在类本身以外实例化

        private static readonly DotNetSigleton instance = new DotNetSigleton();

        //由于 Singleton 实例被私有静态成员变量引用，因此在类首次被对Instance属性的调用所引用之前，不会发生实例化。

        private DotNetSigleton(){}

        public static DotNetSigleton Instance

        {

            get

            {

                return instance;

            }

        }

    }