Modding Tutorials/Setting up a solution

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Modding Tutorials

This page was originally created by Alistaire.

In this tutorial you will learn how to set up a solution, along with instructions on setting the output directory and files for more convenient building right into the Assemblies folder.


Setting up a solution[edit]

Setting up can be different for different IDE's. Feel free to add complete instructions for your IDE of choice.

Visual Studio Community 2022[edit]

NOTE: Visual Studio 2022 is a rather heavy application (2-3 GB for basic functionality) but works out of the box. It is strongly recommended if you are on Windows and have a PC that can handle it. This tutorial is similar for other versions of Visual Studio.

Option 1 (Manual Method):[edit]

  1. Create a new class library project
    1. Once loaded, go to File -> New -> Project...
    2. Type "Class Library (.NET Framework)" in the search bar, and select the C# option.
      Installing the .NET framework
    3. Enter your project name.
    4. Choose a location, preferably:
    5. Enter a solution name (optionally, tick "Place solution and project in the same directory")
    6. Make sure Framework is ".NET Framework 4.7.2"
  2. In your project, set target framework and various other properties
    1. In your Solution Explorer (the panel usually located on the right), right click your project -> Properties (or expand your project and double click "Properties" with the wrench icon)
    2. Optional: Under Application, change your Assembly and Namespace names to anything of your choice
    3. Go to Build -> Advanced... and set "Debugging information" to none
    4. Leave Advanced..., and set the Output Path to "..\..\Assemblies\" (Or wherever the Assemblies folder is)
  3. Add references to RimWorld code
    1. Expand your project in Solution Explorer. Then right click "References" -> Add Reference...
    2. Click Browse...
    3. Navigate towards
      and select files:
    4. Click "Add"
    5. Click "OK" to close the Reference Manager.
    6. Right-click on both Assembly-CSharp.dll and UnityEngine.dll and set Copy Local to False (Properties pane).

Option 2 (Using Nuget):[edit]

This option uses Krafs Rimworld Reference Package it is less involved than using reference assemblies and is the recommended method.

  1. Follow the above up till Add references to RimWorld code
  2. From the Tools menu, select NuGet Package Manager -> Package Manager Settings.
    1. In the Settings dialog, under Package Management, change the Default package management format to PackageReference.
    2. Click OK to close the dialog.
  3. Open Nuget Manager and type Rimworld
  4. Add Krafs Rimworld Reference

You can now continue as if you added the assemblies Doing this makes your project portable, because RimRef can be downloaded by anyone and used from anywhere, unlike Rimworld's assemblies which can't be distributed.

Option 3 (Using Rimworld Dotnet Template):[edit]

This option uses Rimworld Dotnet Template it allows faster creation of mod files including Xml folders

After installing the template.

  1. Open your mod folder
  2. create a new folder for your mod (It is best to use the name you want for your mod)
  3. Open a command prompt in that folder
  4. type dotnet new RimMod (This will create a new mod with the name you specified)
  5. Open the About folder and edit the About.xml file
  6. Open the .sln file in your preferred IDE
  7. Add the rimworld assemblies using your preferred method

While this method is faster, it is still good to know how to do it manually.

Option 4 (Using Cookiecutter):[edit]

This option uses the Rimworld Mod Development Cookiecutter tool.
Note: despite being automatic and potentially taking away some of the tedium away, the environment it sets up is very particular and this tool is currently not recommended for newcomers.
As of Jan 2019, the cookiecutter is set up for Windows development. Linux/Mac people can still use it, but they will have a few errors to clean up.

  1. Open Visual Studio
  2. Once loaded, go to File -> New -> From Cookiecutter...
  3. Search for rimworld
  4. Double-click cookiecutter-rimworld-mod-development
  5. Change the Template Options:
    1. Create To => Your/Rimworld/Mod/Directory
    2. mod_name
    3. namespace_name (don't change if unsure)
    4. author => your steam username
    5. target_version => current RW version (can leave blank for most up-to-date)
    6. in_game_description (not required, can change later in About-Release.xml)
    7. url (can leave blank for link to your Steam Workshop profile)
  6. Click "Create and Open Folder"


Caution: Sharpdevelop (or #develop) does NOT CURRENTLY allow for C# 6.0+ syntax without plugins and does NOT ALLOW for C# 7.0+ syntax at all. For your average project this does not matter, however some existing projects are already built entirely upon C# 6.0+ syntax which can not be compiled anymore in Sharpdevelop. Visual Studio does not have these issues and should be your go-to for compiling large projects such as Combat Extended.

  1. Create a new class library project in your IDE of choice;
    1. Go to File -> New -> Solution;
    2. Go to C# or .NET -> Library or Class Library (NOT portable);
    3. Enter a project name (solution name automatically updated);
    4. Choose a location, preferably:
    5. Optional: Untick "Create a directory for solution"/"Create a project within the solution directory",
  2. In your project, add references to Assembly-CSharp.dll and UnityEngine.dll:
    1. In your IDE project file browser, right-click the "References" folder and "Add reference";
    2. Choose the ".NET Assembly Browser" tab and "Browse...";
    3. Navigate towards
      and select files:
    4. Click "Open" then "OK";
    5. In the References folder, right-click Assembly-CSharp -> Properties and change "Local copy" to False. Do the same for UnityEngine,
  3. In your project properties, change the target framework to .NET 4.7.2:
    1. In your IDE project file browser, right-click "(YourSolutionName)";
    2. Choose Properties;
    3. Go to the "Compiling" tab, "Output", "Target framework", "Change" and choose ".NET Framework 4.7.2",
  4. In your project properties, change the build events so only a single file is built:
    1. Go to the "Compiling" tab, "Output", "Debug info" and choose "No debug information";
    2. Right-click your .cs files -> Properties and change "Copy to output" (If you haven't resized the properties bar, this will be truncated to "Copy to out") to Never,
  5. In your project properties, fix the output location to put the DLL in the Assemblies folder:
    1. Go to the "Compiling" tab, "Output", "Output path" and change the output path to "..\..\Assemblies\".


The setup is similar as the one above. A few special points to address:

  1. Mono 4.X isn't backward compatible so you may need to install an older 3.X version of Mono in order to compile against .NET4.7.2 dlls.
  2. Make sure you uncheck "Use MSBuild build engine (recommended for this project type)" under project > options > build > general (You might find this by right-clicking on your project - not solution - name and selecting options)
  3. Changing the framework to 4.7.2 can be found (for Linux anyway) in the same place.

More detailed installation instructions for Linux can be found here and here. Note that as of now (2021) these may be outdated, so if it doesn't work, you can try the steps described in the Mono section.


On Linux and Mac(?) it is possible to use Mono regardless of IDE (from command line, or if your IDE/editor has build support).

  1. Install Mono (refer to your distribution's instructions);
  2. To build using .csproj files that other setups use, you need the dotnet tool, you can get it by installing the .NET SDK;
  3. If you're starting a new mod and want to use a .csproj file for compatibility with other modders, find e.g. a mod that has description pointing to its GitHub sources and copy from there;
  4. For building use a command like the following (substitute the proper .csproj file and 4.7.2 is the .NET version from the .csproj file):
    FrameworkPathOverride=$(dirname $(which mono))/../lib/mono/4.7.2-api/ dotnet build <project file>.csproj /property:Configuration=Release
  5. If you get errors, it is necessary to edit the .csproj file:
    1. You may need to fix paths (point them to .dll files in RimWorld/RimWorld*_Data/Managed);
    2. See other setups above for other settings (those IDEs write those settings to the .csproj files);

Rider (good for Mac)[edit]

JetBrains Rider is a great cross-platform C# IDE, but it isn't cheap. It's $140 for the first year, including perpetual access to that version (access to future updates gets cheaper, but it's still over $100/year). However, the Early Access versions are a bit unstable but free. They also offer free student licenses.

  1. Open Rider and click New Solution in the welcome dialog.
    1. Click Class Library under .NET on the left. The option may a second to show up.
    2. Under Solution Name (and Project Name), enter the name of your mod.
    3. Set the Solution Directory to [your mod folder]/Source.
    4. Optionally check "put solution and project in the same directory." This is probably a good idea.
    5. Change Framework to .Net Framework 4.7.2.
    6. Click Create.
  2. In the left side bar, expand your solution, right click your project (mod name with "C#" icon) and click Properties.
    1. In the Properties window, select Configurations > Debug on the left and uncheck Debug Symbols.
    2. For both configurations, change the Output Path to ../../Assemblies.
    3. Click OK.
  3. Expand your project, right click References and click Add Reference.
    1. Click Add From.
    2. Browse to the folder with the RimWorld DLLs (Mac: /Users/[username]/Library/Application Support/Steam/steamapps/common/RimWorld/
    3. Select both Assembly-CSharp.dll and UnityEngine.dll and click OK.
    4. Expand Assemblies under References. For both of the assemblies that you just added:
      1. Right click the assembly and click Properties.
      2. Uncheck "Copy Local" (you may need to scroll down) and click OK.

You're done! Note that Rider has a built-in decompiler—to view the source of a RimWorld class or method, just right-click its name and click Go To > Definition.

Visual Studio Code via Dev Container[edit]

VS Code provides with Dev Containers a very simple way to set up an working development environment. To make use of Dev Containers you need VS Code with the Dev Containers Extension and docker installed on your machine.

Quick Start[edit]

For a quick start either clone the repository inside your mods folder:

git clone

or download a zip archive by visiting the Repository. Click "Code", then "Download ZIP" and unzip the code in your mods folder. The Mod has a dependency to Harmony, this one needs also to be in the "Mods" directory. Download the zip and extract it to the "Mods" folder.

Now open the folder with VS Code. If you are not on Linux you need to adjust the path in .devcontainer/docker-compose.yml to your platform. To start up the container you need to press CTRL + Shift + P and type "Dev Container: Reopen in Container". This might take a few minutes. When the container is up and running, switch to the terminal inside VS Code and type:

dotnet build

In the Assemblies folder should now be a "RainingGoo.dll".

Starting a new Project[edit]

To start over with a complete new solution, copy the ".devcontainer" folder to your own project and open it in VS Code.

To create a new solution file in the actual location:

dotnet new sln

To create a new project (here a library) in the actual location:

dotnet new classlib -n MyNewProject -o .

To add the created project to the solution file:

dotnet sln add Path/to/MyNewProject.csproj

For the configuration of the csproj files compare against the example project above.

Common issues[edit]

  • Can't find the option to target .NET Framework 4.7.2? It may require additional installation steps. In Visual Studio, Tools => Get Tools and features => Individual Components => Select .NET Framework 4.7.2 development tools (or google installation instructions). Also make sure your project is a Class Library (.NET Framework). Not .NET Core or .NET Standard.

See also[edit]