NoInlining.cs

using System;
using HarmonyLib;

namespace NoInlining
{
    public class MainClass
    {
        public static void Main(string[] args)
        {
            var harmony = new Harmony("test");
            harmony.PatchAll();
            new Test().Method1();
        }
    }

    [HarmonyPatch(typeof(Test), "Method2")]
    public static class Patch
    {
        static bool Prefix()
        {
            Console.WriteLine("patch");
            return false;
        }
    }

    public class Test
    {
        public void Method1()
        {
            Console.WriteLine("before");
            Method2();
            Console.WriteLine("after");
        }

        public void Method2()
        {
        }
    }
}