问核心+ MongoDb -如何通过“代码”搜索数据库并返回原始url？

EN

    namespace ShortenUrls.Controllers
    {
        [Route("api/codes")]
        public class ShortUrlsController : Controller
        {
            private readonly ShortUrlRepository _repo;

            public ShortUrlsController(ShortUrlRepository repo)
            {
                _repo = repo;
            }

            [HttpGet("{id}")]
            public async Task<IActionResult> Get(string id)
            {
                var su = await _repo.GetAsync(id);

                if (su == null)
                    return NotFound();

                return Ok(su);
            }
            [HttpPost]
            public async Task<IActionResult> Create([FromBody] ShortUrl su)
            {
                await _repo.CreateAsync(su);
                return Ok(su);
            }
}

namespace ShortenUrls.Models.Repository
{
public class ShortUrlRepository
{
    private const string alphabet = "23456789bcdfghjkmnpqrstvwxyz-_";

    private static readonly Random rand = new Random();

    private readonly Database _db;

    public ShortUrlRepository(Database db)
    {
        _db = db;
    }

    private static string GenerateCode()
    {
        const int codeLength = 12;

        var chars = new char[codeLength];

        for (var i = 0; i < codeLength; i++)
        {
            chars[i] = alphabet[rand.Next(0, alphabet.Length)];
        }

        return new string(chars);
    }


    public Task<ShortUrl> GetAsync(string id)
    {
        var objId = ObjectId.Parse(id);

        return _db.Urls.Find(x => x.Id == objId).FirstOrDefaultAsync();
    }

    public Task CreateAsync(ShortUrl su)
    {
        su.Code = GenerateCode();
        return _db.Urls.InsertOneAsync(su);
    }
}