public class Singleton<T> where T : class, new()
{

    private static T m_Instance;
    public static T Instance
    {
        get
        {
            if (m_Instance == null)
            {
                m_Instance = new T();
            }
            return m_Instance;
        }
    }

    ~Singleton()
    {
        m_Instance = null;
    }

    public static bool IsValid()
    {
        return m_Instance != null;
    }

    public static void Destroy()
    {
        m_Instance = null;
    }
}