static void Main(string[] args)
{
int num = 10;
M1(num);
Console.WriteLine(num);//10 值传递：传递的是栈中内容
string name = "nxd";
M2(name);
Console.WriteLine(name);//nxd
Person p = new Person { Name = "123" };
M3(p);
Console.WriteLine(p.Name);//234
M4(ref num);
Console.WriteLine(num);//11 ref引用传递，传递的是栈本身的地址，不是栈中的内容
Console.ReadKey();
}
static void M3(Person p)
{
p.Name = "234";
}