C#中关键字ref修饰类对象或结构体[转]

 using System;
 using System.Collections.Generic;
 using System.Text;
 namespace CSharpTest
 {
     struct Dog
     {
         public int _nFeet;
         public string _sound;
         public Dog(int n, string sound)
         {
             _nFeet = n;
             _sound = sound;
         }
         public int NFeet
         {
             get { return _nFeet; }
             set { _nFeet = value; }
         }
         public string Sound
         {
             get { return _sound; }
             set { _sound = value; }
         }
         public string ToString()
         {
             return String.Format("The dog has {0} feet, and sounds {1}.",
                 _nFeet.ToString(), _sound);
         }
     }
     class Cat
     {
         private int _nFeet;
         private string _sound;
         public Cat(int n, string sound)
         {
             _nFeet = n;
             _sound = sound;
         }
         public int NFeet
         {
             get { return _nFeet; }
             set { _nFeet = value; }
         }
         public string Sound
         {
             get { return _sound; }
             set { _sound = value; }
         }
         public string ToString()
         {
             return String.Format("The cat has {0} feet, and sounds {1}.",
                 _nFeet.ToString(), _sound);
         }
     }
     class Program
     {
         static void Main(string[] args)
         {
             // Cat
             Cat cat = new Cat(, "miao~");
             System.Console.WriteLine(cat.ToString());
             BeatCat(cat);
             System.Console.WriteLine(cat.ToString());
             BeatCat2(ref cat);
             System.Console.WriteLine(cat.ToString());
             System.Console.WriteLine();
             // Dog
             Dog dog = new Dog(, "wang!");
             System.Console.WriteLine(dog.ToString());
             BeatDog(dog);
             System.Console.WriteLine(dog.ToString());
             BeatDog2(ref dog);
             System.Console.WriteLine(dog.ToString());
         }
         public static void BeatCat(Cat cat)
         {
             cat.NFeet = ;
             cat.Sound = "wang~";
         }
         public static void BeatCat2(ref Cat cat)
         {
             cat.NFeet = ;
             cat.Sound = "huhu~";
         }
         public static void BeatDog(Dog dog)
         {
             dog.NFeet = ;
             dog.Sound = "miao!";
         }
         public static void BeatDog2(ref Dog dog)
         {
             dog.NFeet = ;
             dog.Sound = "huhu!";
         }
     }
 }