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

namespace Demo
{
    class Program
    {
        static void ShowDouble(ref int val)
        {
            val *= 2;
            Console.WriteLine("val doubled = {0}", val);
        }

        static void Main(string[] args)
        {
            int val = 5;
            Console.WriteLine("val = {0}", val); // 5
            ShowDouble(ref val); // 同一个内存,10
            Console.WriteLine("val = {0}", val); // 10
            Console.ReadKey();
        }
    }
}

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

namespace Demo
{

    class Program
    {
        static int val;
        static void ShowDouble()
        {
            val *= 2;
            Console.WriteLine("val doubled = {0}",val);
        }

        static void Main(string[] args)
        {
            val = 5;
            Console.WriteLine("val = {0}",val); // 5
            ShowDouble(); // 同一个内存,10
            Console.WriteLine("val = {0}", val); // 10
            Console.ReadKey();
        }
    }
}

这两段代码效果一样，引用的都是同一个变量！