Adding a Game

Describes how to add a game to the Nexus Mods app.

To have a game be automatically recognised by the Nexus Mods app, create a class that inherits from AGame.

Example Game (Click to Expand)

public class Sifu : AGame, ISteamGame, IEpicGame
{
    // Name of your game.
    public override string Name => "Sifu";

    // Game 'Domain' on Nexus, i.e. https://www.nexusmods.com/sifu is 'sifu'
    public override GameDomain Domain => GameDomain.From("sifu");

    // Path to EXE
    public override GamePath GetPrimaryFile(GameStore store) => new(LocationId.Game, "Sifu.exe");

    // [ISteamGame] Steam ID
    // Extract this from SteamDB e.g. https://steamdb.info/app/2138710/ or your `appmanifest_` files in `SteamApps`.
    public IEnumerable<uint> SteamIds => new[] { 2138710u };

    // [IEpicGame] 'CatalogItemId' from JSON,
    // see https://github.com/erri120/GameFinder/wiki/Epic-Games-Store
    public IEnumerable<string> EpicCatalogItemId => new[] { "c80a76de890145edbe0d41679dbccc66" };

    public Sifu(IServiceProvider serviceProvider) : base(serviceProvider) { }

    // Registers supported 'Mod Installers'
    protected override IEnumerable<IModInstaller> MakeInstallers(IServiceProvider provider) => new[] { new SifuModInstaller(provider) };

    // Boilerplate for games that don't do anything special. //
    protected override IReadOnlyDictionary<LocationId, AbsolutePath> GetLocations(IFileSystem fileSystem,
        GameLocatorResult installation)
    {
        return new Dictionary<LocationId, AbsolutePath>()
        {
            { LocationId.Game, installation.Path },
        };
    }

    public override List<IModInstallDestination> GetInstallDestinations(IReadOnlyDictionary<LocationId, AbsolutePath> locations)
        => ModInstallDestinationHelpers.GetCommonLocations(locations);
}

Making the App Auto-Detect Your Game

To add automatic detection for a given game, make your AGame implement the following interfaces (where applicable).

Store	Interface Name	Where to manually find store specific 'App ID'(s)
EA Desktop	IEADesktopGame	It's complicated.
Epic	IEpicGame	Extract CatalogItemId from JSON file in C:\Program Data\Epic\EpicGamesLauncher\Data\Manifests. Reference docs.
GOG Galaxy	IGogGame	Go to HKEY_LOCAL_MACHINE\Software\GOG.com\Games in registry and grab from gameID field. Reference docs.
Origin	IOriginGame	Get from .mfst file in C:\Program Data\Origin\LocalContent. Copy paste everything after ?id=.
Steam	ISteamGame	Extract 'AppId' from SteamDB (Example). Or your appmanifest_{AppId}.acf files in SteamApps folder.
Xbox	IXboxGame	Find inside appxmanifest.xml in game folder. Extract from Name field under Identity.

Quickly Finding the 'App IDs'

Builds of the Nexus Mods app in Debug configuration will print all found games.

[DEBUG] Found Steam Game: 252950, Rocket League
[DEBUG] Found Steam Game: 389730, TEKKEN 7
[DEBUG] Found Steam Game: 71340, Sonic Generations

So if you have the game you want to add support for installed, you can find the needed 'id' in the log.

In that scenario, to implement Rocket League, you would inherit ISteamGame and add 252950 as the ID.

public IEnumerable<uint> SteamIds => new[] { 252950u };

If you have a game that's not tied to a particular store, you'll probably need to extend the AGameLocator class to implement the logic to 'find' your game.

Populating Game Paths

You need to tell the app where to look for files by overriding GetLocations.

Example:

protected override IReadOnlyDictionary<LocationId, AbsolutePath> GetLocations(IFileSystem fileSystem, GameLocatorResult installation)
{
    return new Dictionary<LocationId, AbsolutePath>
    {
        { LocationId.Game, installation.Path },
        { LocationId.AppData, fileSystem.GetKnownPath(KnownPath.LocalApplicationDataDirectory).Combine("Skyrim") }
    };
}

Here we add the game folder and AppData folder to Skyrim LE.

When you are overwriting GetLocations, you should include all paths that the app needs to track, i.e. Saves, Configs, Game Folder etc.

The function GetPrimaryFile is the game's main executable (not a launcher).

Sometimes games on different storefronts may have different locations. For example, a game installed via GOG might have a different save path than the Steam installation.

Linking your Game with NexusMods

To link your game with a Nexus page, you need to set the 'Domain' field.

Each AGame instance has a field named Domain. This Domain corresponds to the URL used on Nexus Mods for the game.

So for example, if you have https://www.nexusmods.com/sifu, you should set the value to sifu

public override GameDomain Domain => GameDomain.From("sifu");

Add your Game to the Dependency Injection Container

For the App to recognise your game, you'll need to add it to the Dependency Injection container.

More specifically, you will need to register your IGame in your project's Services.cs file (create it if it doesn't exist).

public static IServiceCollection AddSifu(this IServiceCollection serviceCollection)
{
    serviceCollection.AddAllSingleton<IGame, Sifu>();
    serviceCollection.AddAllSingleton<IModInstaller, SifuModInstaller>();
    return serviceCollection;
}

After that, you may also need to add it to AddApp and call services.AddYourGame().

General Guidelines

You Might want to Group Similar Games in One Project

If your code targets a specific common 'game engine' or middleware, you might want to put your logic there.

For example, the Nexus Mods app has NexusMods.Games.BethesdaGameStudios, which contains code for the Creation engine.

This code is used by games such as Skyrim LE and Skyrim SE, so these two games live in the NexusMods.Games.BethesdaGameStudios project.