单例模式的特点：
确保一个类只有一个实例,并提供一个全局访问点。

 //单例模式的实现internal class Boss{//定义静态变量保存实例private static Boss uniqueBoss;//定义锁，确保线程访问安全private static readonly object _lock = new object();//定义私有构造函数，使外界不能创建该类实例private Boss(){}//定义公有方法提供一个全局访问点，public static Boss GetBoss(){//关键代码加锁lock (_lock){//如果类的实例不存在则创建，否则直接返回if (uniqueBoss == null){uniqueBoss = new Boss();}}return uniqueBoss;}}//双判断模式的写法：internal class Person{private Person() { }private static Person _instance;private static readonly object _instanceLock = new object();public static Person Instance(){if (_instance == null){lock (_instanceLock){if (_instance == null){_instance = new Person();}}}return _instance;}}

实际使用：

 partial class Singleton_ViewModel : ObservableObject{//创建很多个Boss变量Boss boss_1 = Boss.GetBoss();Boss boss_2 = Boss.GetBoss();Boss boss_3 = Boss.GetBoss();[ObservableProperty]private string name;[ObservableProperty]private int age;[ObservableProperty]private string sex;[RelayCommand]private void Li(){Name = boss_1.Name = "李总";Age = boss_1.Age = 38;Sex = boss_1.Sex = "男";Boss1 = boss_1 == boss_2 ? "boss_1 = boss_2" : "boss_1 != boss_2";}[RelayCommand]private void Xie(){Name = boss_2.Name = "谢总";Age = boss_2.Age = 56;Sex = boss_2.Sex = "女";Boss2 = boss_1 == boss_2 ? "boss_1 = boss_2" : "boss_1 != boss_2";}[RelayCommand]private void Zhang(){Name = boss_3.Name = "张总";Age = boss_3.Age = 29;Sex = boss_3.Sex = "男";Boss3 = boss_2 == boss_3 ? "boss_2 = boss_3" : "boss_2 != boss_3";}[ObservableProperty]private string boss1;[ObservableProperty]private string boss2;[ObservableProperty]private string boss3;[RelayCommand]private void t1(){Task.Run(() =>{while (true){Li();Task.Delay(1000);}});}[RelayCommand]private void t2(){Task.Run(() =>{while (true){Xie();Task.Delay(1500);}});}[RelayCommand]private void t3(){Task.Run(() =>{while (true){Zhang();Task.Delay(2000);}});}}