引用类型对象

using System;
using System.Collections.Generic;
using System.Linq;
using System.Data;
using System.Text;
using System.Threading.Tasks;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            Attendance a = new Attendance("aaa");
            AA(a);
            Console.WriteLine(a.Name);
            Console.ReadLine();
        }

        public static  void AA( Attendance a)
        {
            //a = new Attendance("dddd");
            a.Name = "eee";
        }
    }

    public class Attendance
    {
        public Attendance(string Name)
        {
            this.Name = Name;
        }
        public string Name { get; set; }
        public DateTime AttendanceDate { get; set; }
    }
}

  class Program
    {
        static void Main(string[] args)
        {
            Attendance a = new Attendance("aaa");
            AA(a);
            Console.WriteLine(a.Name);
            Console.ReadLine();
        }

        public static  void AA( Attendance a)
        {
            a = new Attendance("dddd");
            //a.Name = "eee";
        }
    }

 class Program
    {
        static void Main(string[] args)
        {
            Attendance a = new Attendance("aaa");
            AA(a);
            Console.WriteLine(a.Name);
            Console.ReadLine();
        }

        public static  void AA( Attendance a)
        {
            a = new Attendance("dddd");
            a.Name = "eee";
        }
    }

 class Program
    {
        static void Main(string[] args)
        {
            Attendance a = new Attendance("aaa");
            AA(a);
            Console.WriteLine(a.Name);
            Console.ReadLine();
        }

        public static  void AA( Attendance a)
        {
            a.Name = "eee";
            a = new Attendance("dddd");
        }
    }

 class Program
    {
        static void Main(string[] args)
        {
            Attendance a = new Attendance("aaa");
            AA(ref a);
            Console.WriteLine(a.Name);
            Console.ReadLine();
        }

        public static  void AA( ref Attendance a)
        {
            a.Name = "eee";
            a = new Attendance("dddd"); 
        }
    }