using Harmony;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;
using System.Threading.Tasks;
​
namespace ConsoleApp44
{
    class Program
    {
        static void Main(string[] args)
        {
            HarmonyInstance instance = HarmonyInstance.Create("test");
​
            Type self = typeof(Program);
            var targetMethod = self.GetMethod(nameof(Target));
            MethodInfo patchMethod = ResolveDynamicPatch(self);
            instance.Patch(targetMethod, new HarmonyMethod(patchMethod));
​
            Target();
            Console.ReadLine();
        }
​
        private static MethodInfo ResolveStaticPatch(Type self)
        {
            var patchMethod = self.GetMethod(nameof(Prefix));
            return patchMethod;
        }

        private static MethodInfo ResolveDynamicPatch(Type self)
        {
            MethodInfo consoleWriteLine = typeof(Console).GetMethod("WriteLine", new Type[] {typeof(String)});
​
            Type returnType = typeof(void);
            Type[] parameterTypes = new Type[0];
            DynamicMethod dynamicMethod = new DynamicMethod("MyMethod", returnType, parameterTypes);
​
            var il = dynamicMethod.GetILGenerator();
            il.Emit(OpCodes.Ldstr, "hello world");
            il.EmitCall(OpCodes.Call, consoleWriteLine, null);
            il.Emit(OpCodes.Ret);
​
            DelegateTypeFactory factory = new DelegateTypeFactory();
            Type delegateType = factory.CreateDelegateType(dynamicMethod);
​
            var method = delegateType.GetMethod("Invoke") ?? throw new ArgumentException();
            return method;
        }
​
        public static void Target()
        {
​
        }
​
        public static void Prefix()
        {
            Console.WriteLine("hello");
        }
    }
}