C# sealed 修饰符标识禁止其他类继承

using System;

namespace ConsoleApp37
{
    class Program
    {
        static void Main(string[] args)
        {
        }
    }

    // sealed 修饰符标识禁止其他类继承
    public sealed class User
    {
        public string Name { get; set; }

        public string Sex { get; set; }
    }

    // 继承 User 出错
    public class User2 : User
    {

    }
}