Implementing Additional Methods

Surely you should be able to implement new functions addition to existing one if you need it. This is SOLID after all! Let's see how we can do this. First you need to create the interface that inherits from IRENCache interface. Your new interface should contain additional methods and must be inherited from IRENCache interface to get all function signatures:

public interface IMyCacheService: IRENCacheService
{
    Task<T> GetSingleAsync<T>(string cacheKey, Func<T,bool> predicate, CancellationToken cancellationToken = default);
}

Then create your custom CacheService class and make it inherit from RENRedisCacheService class and your new interface (in this case it is IMyCacheService) that contains your custom function signature.

public class MyCacheService : RENRedisCacheService, IMyCacheService
{
    public MyCacheService(IConnectionMultiplexer connection, IConfiguration configuration) : base(connection, configuration) { }
    
    public async Task<T> GetSingleAsync<T>(string cacheKey, Func<T,bool> predicate, CancellationToken cancellationToken = default);
    {
        Console.WriteLine("Getting single custom...");
        // custom implementations
        return (await base.GetAsync<IEnumerable<T>>(cacheKey, cancellationToken)).SingleOrDefault(predicate);
    }
}

Then you have to change your register type in Program.cs to this since you will want to use IMyCacheService from now on:

// builder.Services.RegisterRENCacheAccessHelpers<MyCacheService>();
builder.Services.AddScoped<IMyCacheService, MyCacheService>();

Then you can use this custom function as follows:

public class HomeController : ControllerBase
{
    private readonly IMyCacheService _customCacheService;
    private readonly IRENRepository<User> _userRepository;

    public HomeController(IRENUnitOfWork<RENDbContext> uow, IMyCacheService customCacheService)
    {
        _userRepository = uow.GetRENRepository<User>();
        _customCacheService = customCacheService;
    }

    [HttpGet]
    [Route("GetUser")]
    public async Task<IActionResult> Index([FromQuery] int Id)
    {
        var cacheKey = $"users_{Id}";
        var user = await _customCacheService.GetAsync<User>(cacheKey);
        if (user != null) return Ok(user);

        var allUsersCacheKey = "users";
        user = await _customCacheService.GetSingleAsync<User>(allUsersCacheKey, _ => _.Id == Id);
        if (user != null) return Ok(user);

        user = await _userRepository.GetSingleAsync(_ => _.Id == Id);
        await _customCacheService.SetAsync(cacheKey, user);

        return Ok(user);
    }
}