In this post, I’ll walk through the complete solution we ended up using. If you’re looking to publish a MonoGame project on Steam, this might save you some time.

General Setup

I assume you already have a working .NET 6+ (MonoGame) project and the corresponding SDK installed. You’ll also need a Steamworks developer account to access the Steamworks SDK.

To make platform-specific builds easier, define platform detection constants in your .csproj file:

<PropertyGroup>
  <IsWindows Condition="'$(RuntimeIdentifier)' == 'win-x64' or ('$(RuntimeIdentifier)' == '' and $([MSBuild]::IsOSPlatform('Windows')))">true</IsWindows>
  <IsOSX Condition="'$(RuntimeIdentifier)' == 'osx-x64' or ('$(RuntimeIdentifier)' == '' and $([MSBuild]::IsOSPlatform('OSX')))">true</IsOSX>
  <IsLinux Condition="'$(RuntimeIdentifier)' == 'linux-x64' or ('$(RuntimeIdentifier)' == '' and $([MSBuild]::IsOSPlatform('Linux')))">true</IsLinux>
  
  <IsWindows Condition="'$(IsWindows)' == ''">false</IsWindows>
  <IsOSX Condition="'$(IsOSX)' == ''">false</IsOSX>
  <IsLinux Condition="'$(IsLinux)' == ''">false</IsLinux>
</PropertyGroup>

Add Steamworks Dependencies

Download the Facepunch.Steamworks library directly from the GitHub releases page and extract the contents of the net6.0 folder into a new folder in your project root called Steamworks.

Also, download the official Steamworks SDK directly from Steamworks. As of writing, SDK version 1.61 works with the latest release of Facepunch.Steamworks. Copy the redistributable binaries (steam_api64.dll, libsteam_api.so, etc.) into the same Steamworks folder.

Your Steamworks/ folder should now include:

Facepunch.Steamworks.Posix.deps.json
Facepunch.Steamworks.Posix.dll
Facepunch.Steamworks.Posix.pdb
Facepunch.Steamworks.Posix.xml
Facepunch.Steamworks.Win64.deps.json
Facepunch.Steamworks.Win64.dll
Facepunch.Steamworks.Win64.pdb
Facepunch.Steamworks.Win64.xml
libsteam_api.dylib
libsteam_api.so
steam_api64.dll

Update the .csproj to reference the Facepunch.Steamworks and native libraries for the correct platform:

<ItemGroup>
  <!-- Reference Facepunch.Steamworks -->
  <Reference Include="Facepunch.Steamworks, Version=2.4.1, Culture=neutral, processorArchitecture=MSIL">
    <SpecificVersion>False</SpecificVersion>
    <HintPath Condition="$(IsWindows)">Steamworks/Facepunch.Steamworks.Win64.dll</HintPath>
    <HintPath Condition="$(IsOSX) or $(IsLinux)">Steamworks/Facepunch.Steamworks.Posix.dll</HintPath>
    <CopyToOutputDirectory>Always</CopyToOutputDirectory>
  </Reference>

  <!-- Include native Steamworks libaries -->
  <Content Include="Steamworks/steam_api64.dll" Condition="$(IsWindows)">
    <Link>steam_api64.dll</Link>
    <CopyToOutputDirectory>Always</CopyToOutputDirectory>
  </Content>

  <Content Include="Steamworks/libsteam_api.dylib" Condition="$(IsOSX)">
    <Link>Lib/libsteam_api.dylib</Link>
    <CopyToOutputDirectory>Always</CopyToOutputDirectory>
  </Content>

  <Content Include="Steamworks/libsteam_api.so" Condition="$(IsLinux)">
    <Link>libsteam_api.so</Link>
    <CopyToOutputDirectory>Always</CopyToOutputDirectory>
  </Content>
</ItemGroup>

If everything is working, you can initialize the Steam API in your code and check the connection.

public void Initialize()
{
    try
    {
        Steamworks.SteamClient.Init(480, true);

        var playername = Steamworks.SteamClient.Name;
    }
    catch (Exception e)
    {
        Debug.WriteLine("{0}", e);
    }
}

Bundling Windows & Linux

Download GameBundle. This neat tool greatly simplifies the bundling process and provides a clean looking folder structure by using NetBeauty internally.

And that is it. You can now use the Steam API and bundle your game for Windows and Linux:

gamebundle -wl -z --mg
# -w: Build for Windows
# -l: Build for Linux
# -z: Zip output
# --mg: Don't move MonoGame's native libraries to the Lib folder

Note that Linux users will need to add the permissions to execute the game.

Bundling macOS

Bundling for macOS is a bit more involved and additionally requires a property list file and a separate icon.

Convert your existing game icon to the icns format and store the new file under Icon.icns directly in the root. Then create a new file called Info.plist also in the project root.

Add the following content to the Info.plist. Replace MyApp with the name of your application and com.example.MyApp with your identifier.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>CFBundleIconFile</key>
    <string>Icon</string>
    <key>CFBundleName</key>
    <string>MyApp</string>
    <key>CFBundleIdentifier</key>
    <string>com.example.MyApp</string>
    <key>CFBundlePackageType</key>
    <string>APPL</string>
    <key>CFBundleVersion</key>
    <string>1.0</string>
    <key>CFBundleShortVersionString</key>
    <string>1.0</string>
</dict>
</plist>

Finally, adjust your .csproj to include them during the build for macOS:

<ItemGroup Condition="$(IsOSX)">
  <Content Include="./Info.plist">
    <CopyToOutputDirectory>Always</CopyToOutputDirectory>
  </Content>
  <Content Include="./Icon.icns">
    <CopyToOutputDirectory>Always</CopyToOutputDirectory>
  </Content>
</ItemGroup>

Now you can also bundle your game for macOS again using GameBundle.

gamebundle -m -bz --mg --nbeauty2
# -m: Bundle for macOS
# -b: Output correct structure and create app bundle for macOS
# -z: Zip output
# --mg: Don't move MonoGame's native libraries to the Lib folder
# --nbeauty2: Use NetBeauty2 instead of NetCoreBeauty

Conclusion

You can now use the Steamworks API in your .Net project and bundle it for Windows, Linux and macOS. Hope this saves you some time.

See the github repository for a basic setup that includes project structure, and configuration files.