public class Account:BaseMongoEntity
{
    public string Name { get; set; }
    public string Mobile { get; set; }
}

public class MyDbService:MongoDbProvider
{
    public MyDbService(IOptionsMonitor<MongoDBOptions> options) : base(options){}
    public IMongoCollection<Account> Account => _database.GetCollection<Account>("Account");
}

public class Startup
{
  public Startup(IConfiguration configuration)
  {
    Configuration = configuration;
  }

  public IConfiguration Configuration { get; }

  public void ConfigureServices(IServiceCollection services)
  {
    services.AddMongoDB<MyDbService>(options =>
    {
      options.ConnectionString = Configuration.GetConnectionString("MongoDbConnection");
    });
    //.....................
  }
}

[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
    private MyDbService _db = null;
    public ValuesController(MyDbService db)
    {
        this._db = db;
    }
    // GET api/values
    [HttpGet]
    public ActionResult<IEnumerable<string>> Get()
    {
        _db.Account.Add(new Account(){Name = "张三",Mobile = "13812345678"});
        return new string[] { "value1", "value2" };
    }
}

public class Account:BaseMongoEntity
{
    public string Name { get; set; }
    public string Mobile { get; set; }
}

public class MyDbService:MongoDbProvider
{        
    public MyDbService(string conn):base(conn){}
    //public MyDbService(IOptionsMonitor<MongoDBOptions> options) : base(options){}
    public IMongoCollection<Account> Account => _database.GetCollection<Account>("Account");
}

[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
    // GET api/values
    [HttpGet]
    public ActionResult<IEnumerable<string>> Get()
    {
        var db = new MyDbService("mongodb://user:pwd@xxx.xxx.xxx.xxx:27017/testdb?authSource=admin");
        db.Account.Add(new Account(){Name = "张三",Mobile = "13812345678"});
        return new string[] { "value1", "value2" };
    }
}