private static void Main(string[] args)
{
Test1 t1 = new Test1(100);
Console.Write("初始");
t1.DisplayValue();
Console.Write("修改后");
int x = t1.value;
x = 200;
t1.DisplayValue();
Test2 t2 = new Test2(100);
Console.Write("初始");
t2.DisplayValue();
Console.Write("修改后");
ref int y = ref t2.value;