Modding Tutorial : Use Harmony to patch game's dll

Modding Tutorial : Use Harmony to patch game's dll

Hi everyone,

I'm proud to present to you a small tutorial on how to use Harmony (https://github.com/pardeike/Harmony) to patch the game's dll to add/modify game's features.

STEP 0 : Prerequisites

• Visual studio 2017 or higher. Community (it's free !) works too. Free version available here : https://visualstudio.microsoft.com/fr/vs/
  
• .NET Frameworks 3.5 installed (you should be able to select this version when installing Visual Studio)
  
• Last version of dnSpy (see STEP 1)
  
• Last version of Harmony  : https://github.com/pardeike/Harmony/releases
  

STEP 1 : Preparing the game's dll to load a mod dll

1] Get the last version of dnSpy here : https://github.com/0xd4d/dnSpy/releases

I advise you to get the "dnSpy-netcore-win64.zip" file, as your computer may not have the correct .NET Framework installed

2] Extract dnSpy in a folder, then launch "dnSpy.exe"

3] With dnSpy, open the game dll located at "GameFolder\ProjectHospital_Data\Managed\Assembly-CSharp.dll"

[If you are not used to modifying a dll on the fly with dnSpy, you can skip now and go to step 2. Patched dll download links are provided in the next post of this one]

4] In the dll main namespace, look for TitleScreenController class

5] Overwrite LoadAddons method code with the following code : https://pastebin.com/UbM1whPD

This patched method allows the game's mod loader to look if a mod folder contains a Harmony dll and a ModName.dll and load it.

6] Hit "Save all" button (CTRL+SHIFT+S)

STEP 2 : Set up the mod folder

1] Create a new folder in "GameFolder\ProjectHospital_Data\StreamingAssets\Addons\", named after your mod name. Be sure this name does not contain any space characters.

2] Inside this folder, copy 0Harmony.dll

3] With Visual Studio (Community) create a new Class Library inside the newly created mod folder, named after your mod name (the same name of the previously created folder).

4] Open the AssemblyInfo.cs file and remove the following fields :

• AssemblyTitle
  
• AssemblyFileVersion
  
• AssemblyVersion
  

5] Delete "Class1.cs" solution's file

6] Create a new class named "ModEntryPoint.cs" and paste the following code : https://pastebin.com/kzw3fQ70

7] Replace <modname>, <modversion>, <gameversion> and <yourpseudo> occurrences with relevant data

8] Inside project's references, add the following references :

• 0Harmony.dll
  
• UnityEngine.CoreModule.dll (GameFolder\ProjectHospital_Data\Managed\)
  
• Assembly-CSharp.dll (GameFolder\ProjectHospital_Data\Managed\)
  

9] Inside Project's Settings, change the Application > Build > Output path (both for Debug and Release configurations) to

Code:

..\

10] Hit compile to check if everything is alright

11] Inside your mod folder, you should now have two dll : 0Harmony.dll and YourMod.dll (see the following screenshot for reference)



12] Congrats, your mod folder and solution are correctly setup !

STEP 2 : Read the game's dll

1] Using dnSpy, read trough game's dll to locate interesting methods

STEP 3 : Use Harmony patches (Prefix and Postfix methods) to modify the game's features

1] Harmony API : https://harmony.pardeike.net/articles/intro.html

2] See my mod "Doctor Mode : Perks and Cost" as a working example on how to patch game's methods (Link : https://projecthospital.forumotion.com/t2449-modharmony-doctor-mode-perks-and-cost#8862 )

If you have coding question, feel free to use this thread to ask !

Patched Assembly

Download the corresponding archive and extract the dll inside YourGameFolder\ProjectHospital_Data\Managed

• 1.2.19.532 hotfix1(last update)
  
• 1.2.19.532
  

Is this tutorial actual?

mishelle89 wrote:Is this tutorial actual?

Hi, we're currently working on an official support for Harmony, so I plan to put together an up to date guide in the next few days.

Btw, thanks to @PanzerKadaver for leading the way!

jan.oxymoron wrote:

mishelle89 wrote:Is this tutorial actual?

Hi, we're currently working on an official support for Harmony, so I plan to put together an up to date guide in the next few days.

Btw, thanks to @PanzerKadaver for leading the way!

Sounds good! It would be nice to know name of entry point at least. I tried with "ModEntryPoint", but looks like Start() never called.
Any way I will wait for official tutorial

mishelle89 wrote:

jan.oxymoron wrote:

mishelle89 wrote:Is this tutorial actual?

Hi, we're currently working on an official support for Harmony, so I plan to put together an up to date guide in the next few days.

Btw, thanks to @PanzerKadaver for leading the way!

Sounds good! It would be nice to know name of entry point at least. I tried with "ModEntryPoint", but looks like Start() never called.
Any way I will wait for official tutorial

Hi, you'd still need to modify the game's dll according to the original guide to add the mod-loading code, but I think at this point it's worth it to wait for the official support in the upcoming patch.