✅ .NET Core N-Tier API Project question about repository pattern.

[HttpGet]
public async Task<ActionResult<TodoList>> Get(int id)
{
    var query = new GetTodoListQuery()
    {
        Id = id
    };

    var result = await _mediator.Send(query);
    if (!result.IsSuccess)
    {
        return result.Error switch
        {
            NotFoundError notFoundError => NotFound(notFoundError.Message),
            ValidationError validationError => BadRequest(validationError.ValidationFailures),
            _ => Problem(detail: result.Error.Message, title: "Internal Server Error", statusCode: 500)
        };
    }

    // return _mapper.Map<TodoListDto>(result.Entity);

    return result.Entity;
}

[HttpGet]
public async Task<ActionResult<TodoList>> Get(int id)
{
    var query = new GetTodoListQuery()
    {
        Id = id
    };

    var result = await _mediator.Send(query);
    if (!result.IsSuccess)
    {
        return result.Error switch
        {
            NotFoundError notFoundError => NotFound(notFoundError.Message),
            ValidationError validationError => BadRequest(validationError.ValidationFailures),
            _ => Problem(detail: result.Error.Message, title: "Internal Server Error", statusCode: 500)
        };
    }

    // return _mapper.Map<TodoListDto>(result.Entity);

    return result.Entity;
}

public class GetTodoListQueryHandler : IRequestHandler<GetTodoListQuery, Result<TodoList>>
{
    public async Task<Result<TodoList>> Handle(GetTodoListQuery request, CancellationToken cancellationToken)
    {
        if (request is null)
        {
            return Result<TodoList>.FromError(new ArgumentNullError(nameof(request)));
        }

        // validate query
        var validator = new GetTodoListQueryValidator();
        var validationResult = await validator.ValidateAsync(request, cancellationToken);

        if (!validationResult.IsValid)
        {
            return new ValidationError(validationResult.Errors);
        }

        var list = FakeDB.Instance.TodoLists.FirstOrDefault(x => x.Id == request.Id);

        return list ?? Result<TodoList>.FromError(new NotFoundError());
    }
}

public class GetTodoListQueryHandler : IRequestHandler<GetTodoListQuery, Result<TodoList>>
{
    public async Task<Result<TodoList>> Handle(GetTodoListQuery request, CancellationToken cancellationToken)
    {
        if (request is null)
        {
            return Result<TodoList>.FromError(new ArgumentNullError(nameof(request)));
        }

        // validate query
        var validator = new GetTodoListQueryValidator();
        var validationResult = await validator.ValidateAsync(request, cancellationToken);

        if (!validationResult.IsValid)
        {
            return new ValidationError(validationResult.Errors);
        }

        var list = FakeDB.Instance.TodoLists.FirstOrDefault(x => x.Id == request.Id);

        return list ?? Result<TodoList>.FromError(new NotFoundError());
    }
}