AccessTools.Field: Could not find field for type System.Diagnostics.StackFrame and name methodAddress

[kmai-universe]

Hi,

I'm trying to use Harmony to patch a Unity project from 2016 which uses MONO 2.0. I use the .NET 3.5 version of Harmony 2.4.2.0 but keep getting this error on any patch method that i try to implement:

`

Harmony id=harmony.vrcoaster, version=2.4.2.0, location=\Managed\0Harmony.dll, env/clr=2.0.50727.1433, platform=Win32NT

AccessTools.Method: Could not find method for type System.Exception and name PrepForRemoting and parameters

Started from static System.Void Universe.IT.Modding.Loader::OnLoad(), location \Managed\vrcoaster-mod.dll

At 2026-01-22 08.49.21

AccessTools.Field: Could not find field for type System.Diagnostics.StackFrame and name methodAddress

Patch: System.Void Smaaash.GeneralOperations::LaunchAppropriate()

Replacement: static System.Void Smaaash.GeneralOperations::Smaaash.GeneralOperations.LaunchAppropriate_Patch1(Smaaash.GeneralOperations this)

IL_0000: // start original
IL_0000: ldsfld Smaaash.Hardware Smaaash.Grid::hardware
IL_0005: ldfld Smaaash.WhatAmI Smaaash.Hardware::whatAmI
IL_000A: ldc.i4.1
IL_000B: bne.un => Label0
IL_0010: ldstr "DrawKiosk"
IL_0015: call static System.Void UnityEngine.Application::LoadLevel(System.String name)
IL_001A: br => Label3
IL_001F: Label0
IL_001F: ldsfld Smaaash.Hardware Smaaash.Grid::hardware
IL_0024: ldfld Smaaash.WhatAmI Smaaash.Hardware::whatAmI
IL_0029: ldc.i4.2
IL_002A: bne.un => Label1
IL_002F: ldstr "OperatorKiosk"
IL_0034: call static System.Void UnityEngine.Application::LoadLevel(System.String name)
IL_0039: br => Label4
IL_003E: Label1
IL_003E: ldsfld Smaaash.Hardware Smaaash.Grid::hardware
IL_0043: ldfld Smaaash.WhatAmI Smaaash.Hardware::whatAmI
IL_0048: brtrue => Label2
IL_004D: ldstr "Oculus"
IL_0052: call static System.Void UnityEngine.Application::LoadLevel(System.String name)
IL_0057: br => Label5
IL_005C: Label2
IL_005C: ldarg.0
IL_005D: ldfld UnityEngine.UI.Text Smaaash.GeneralOperations::whoMsg
IL_0062: ldstr "Development Error?\nStrange problem with ID Files."
IL_0067: callvirt virtual System.Void UnityEngine.UI.Text::set_text(System.String value)
IL_006C: // end original
IL_006C: Label3
IL_006C: Label4
IL_006C: Label5
IL_006C: nop
IL_006D: call static System.Void Universe.IT.Modding.GeneralOperations_LaunchAppropriate_patch::Postfix()
IL_0072: ret
DONE
`

It does not matter what method i try to patch, they will all crash the mod with the same "AccessTools.Field: Could not find field for type System.Diagnostics.StackFrame and name methodAddress".

My project is set to .NET framework 4.7.2

Is it just not possible to use Harmony 2 for old unity project running MONO 2.0?

[pardeike]

It does not matter much what you set in your project. You need to check what the runtime is when the code executes. Unity can deploy games in two fundamental ways: with Net Framework support and only Net Standard which does not include the libraries Harmony needs because it strips away everything that is needed to do dynamic code generation and related things. If you open the game assemblies with a decompiler like dnSpy or ILSpy it will show you what dependencies the main module has and that can help you determine the runtime (but best would be to add some code to your mod that logs the actual runtime).

Harmony tests with all kind of net versions including Mono so I am pretty confident it supports Mono in general.

[pardeike]

Also please always post the full exception stacktrace.

[kmai-universe]

It does not matter much what you set in your project. You need to check what the runtime is when the code executes. Unity can deploy games in two fundamental ways: with Net Framework support and only Net Standard which does not include the libraries Harmony needs because it strips away everything that is needed to do dynamic code generation and related things. If you open the game assemblies with a decompiler like dnSpy or ILSpy it will show you what dependencies the main module has and that can help you determine the runtime (but best would be to add some code to your mod that logs the actual runtime).

Harmony tests with all kind of net versions including Mono so I am pretty confident it supports Mono in general.

Hi, thanks for the quick reply!

I forgot to mention one important factor; it works without issue with Harmony 1.2.1. it's only when i try to use harmony 2 that i get the above mentioned errors. I'd like to use the latest Harmony for the remote debugging possibilities.

If i open the Assembly-csharp.dll in dnSpy then it says .NET Framework 3.5 and x64 architecture.
If i right click mscorlib.dll in the Managed folder then it says MONO Common Language Runtime version 2.0.50727.1433.

Also please always post the full exception stacktrace.

I'm not sure how i do that? Is there any way for me to catch the exception and log it when the game crashes?

[pardeike]

I won't comment on Harmony 1 since it's long obsolete and unsupported.

Regarding the stack trace you need to figure this out yourself - I cannot support all games and environments that are out there - simply too many.