SingleOrDefault抛出＆＃34; Sequence包含多个元素＆＃34;当用主键查询时

Question

我遇到了一个时髦的问题，.SingleOrDefaultAsync在我不期待的时候会发出错误。我的表格为Thing，主键为varchar ThingId。

我的代码类似如下：

IDbSet<Thing> Things;  // initialized by dependency injection
...

public async Task<Thing> FindThingById(string thingId)
{
    return await Things.SingleOrDefaultAsync(o => o.ThingId == thingId).ConfigureAwait(false);
}

关于如何返回多个结果的任何想法，从而抛出一个异常说'Sequence contains more than one element' ??

当我运行SQL查询时：

SELECT * FROM Things where ThingId = '1234'

我得到了一个预期的结果。

编辑（调用代码）：

public sealed partial class ThingDetailsManager : IThingDetailsManager
    {
        private readonly IThingRepository _thingRepository;
        private readonly IThingDetailsSerializer _thingDetailsSerializer;

        public async Task<ThingDetails> FetchThingDetails(string thingId)
        {
            var thing = await _orderRepository.FindThingById(thingId).ConfigureAwait(false);

            if (thing == null)
                return null;

            var thingDetails = _thingDetailsSerializer.Deserialize(thing.ThingDetails);
            thingDetails.SetThingId(thingId);

            return thingDetails;
        }
    }