代码如下：
public class Singleton<T> where T : class { private static T _instance; private static readonly object _lock = new object(); public static T Instance { get { if (_instance == null) { lock (_lock) { if (_instance == null) { _instance = (T)Activator.CreateInstance(typeof(T), true); } } } return _instance; } } }
使用：
public class User : Singleton<User> { private User() { } }