1 class Program
 2     {
 3         static void Main(string[] args)
 4         {
 5 
 6             T t = new T();
 7             t.num = 5;
 8             ChangeT(ref t);
 9             Console.WriteLine(t.num);
10             string str;
11             string result;
12             result = Handle(out str);
13             Console.WriteLine(str);
14             Console.WriteLine(result);
15         }
16 
17         static string Handle(out string s)
18         {
19             s = "hello";
20             return "ok";
21         }
22 
23         static void ChangeT(ref T t)
24         {
25             t.num++;
26         }
27     }