问c# harmony示例未按预期打印注入日志

EN

using System;
using System.Collections.Generic;
using System.Reflection;
using Harmony;

public class Program
{
    public static void Main()
    {
        var harmony = HarmonyInstance.Create("net.example.plugin");
        harmony.PatchAll(Assembly.GetExecutingAssembly());
        Program p = new Program();
        p.Bar();
    }

    [HarmonyPostfix]
    [HarmonyPatch(typeof(Program), "Bar")]
    public static void Postfix_Bar(){ 
        Console.WriteLine("postfix Bar log");  // this never gets printed as expected. 
    }

    [HarmonyPostfix]
    [HarmonyPatch(typeof(Program), "Foo")]
    public static void Postfix_Foo(ref string res){  //however, this gets error res could not be found.  https://github.com/pardeike/Harmony/wiki/Prioritiy-annotations
        Console.WriteLine("postfix Foo log");
        res = "new value";
    }

    public void Bar() {
        Console.WriteLine("Hello World !!! ");
    }

    static string Foo()
    {
        return "secret";
    }
}