The instance of entity type 'Model' cannot be tracked because another instance with the same key value for {'Id'} is already being tracked.

 The instance of entity type 'Model' cannot be tracked because another instance with the same key value for {'Id'} is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached. Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the conflicting key values.

新增数据到数据库后再在同一个方法或请求更新某些字段报的错误，大概的意思就是=>

无法跟踪实体类型“Model”的实例，因为已经在跟踪具有相同键值{'Id'}的另一个实例。在附加现有实体时，请确保只附加一个具有给定键值的实体实例。考虑使用' dbcontexttoptionsbuilder。EnableSensitiveDataLogging'查看冲突的键值。

我的做法是既然同一个链接，那么我就重新弄一个连接出来，因为我这efcore组件封装了，取context有点麻烦。所以选择别的办法。

源代码如下,报错的地方就是@2这里的更新引发错误：

 [HttpPost]
        public async Task SaveData(PushMessageUpdateRequest data)
        {
            if (data == null)
                throw new BusException($"{nameof(PushMessageUpdateRequest)} is null", ErrorCodeDefine.ParameterIsNull);
            if (data.Id.IsNullOrEmpty())
            {
                InitEntity(data);
                foreach (var content in data.Contents)
                {
                    InitEntity(content);
                }
                await _pushMessageBusiness.AddDataAsync(data);
                var res = await _soptBusiness.FirstOrDefault(x => x.BusinessCode == "tttt").GetCustomerPushInfo();
                var groups = res.Where(x => x.Value != null).GroupBy(x => x.Value).ToDictionary(x => x.Key, y => y.Select(x => x.Key).ToList());
                List<bool> pushedFlag = new List<bool> {  };
                foreach (var item in groups)
                {
                    var pushContent = data.Contents.Where(x => x.Lang == item.Key.ToLower()).FirstOrDefault();
                    if (pushContent != null && pushContent.Content.IsNotNullOrEmpty())
                    {
                        if (data.PushTime == null)
                        {
                            var result = await _pushClient.SendPush(new Klickl.Push.Sdk.Model.SendPushRequest
                            {
                                Type = Klickl.Push.Sdk.Model.PushType.Google,
                                Ids = item.Value,
                                NoticeContent = pushContent?.Content,
                                Title = pushContent?.Title,
                                IsApnsProduction = false
                            });
                            pushedFlag.Add(result);
                        }
                        else
                        {
                            JobHelper.SetDelayJob(async () =>
                            {
                                var result = await _pushClient.SendPush(new Klickl.Push.Sdk.Model.SendPushRequest
                                {
                                    Type = Klickl.Push.Sdk.Model.PushType.Google,
                                    Ids = item.Value,
                                    NoticeContent = pushContent?.Content,
                                    Title = pushContent?.Title,
                                    IsApnsProduction = false
                                });
                                pushedFlag.Add(result);
                            }, data.PushTime.Value.Subtract(DateTime.Now));
                        }

                    }
                }

                data.SuccessCount= pushedFlag.Where(x=>x==true).Count();    //@1
                data.PushCount = groups.Count;
                await _pushMessageBusiness.UpdateDataAsync(data);    //@2
            }
            else
            {
                await _pushMessageBusiness.UpdateDataAsync(data);
            }
        }

首先想的是_pushMessageBusiness这个business重新构造一个，像这样@3新增的business，@4就是为了报错加上去的。测试发现还是报一样的错误。

  private readonly IPushMessageBusiness _pushMessageBusiness;  //@3
        private readonly PushClient _pushClient;
        private readonly IEnumerable<ISpotBusiness> _soptBusiness;
        private readonly IAutoPushMessageBusiness _autoPushMessageBusiness;
        private record SaveDataChangeEventArgs(string Id, int SucessCount, int PushCount);    
        private EventHandler<SaveDataChangeEventArgs> SaveDataChangeEventEventHandler;
      
        private readonly IPushMessageBusiness _updataPushMessageBusiness;   @4
        private IServiceScopeFactory _scopeFactory;

 

因为_pushMessageBusiness里面有idbaccessor，及数据库的底层链接，所以上面注入idbaccessor是没问题，可以把bug解决掉，但是这样取原始远不如获取business安全和稳定。

解决办法如下：

                data.SuccessCount= pushedFlag.Where(x=>x==true).Count();
                data.PushCount = groups.Count;
                await _pushMessageBusiness.UpdateDataAsync(data);

上面代码最好独立出来，我通过事件来更新。

   if (groups.Count > 0 && SaveDataChangeEventEventHandler != null)
                    SaveDataChangeEventEventHandler(this, new SaveDataChangeEventArgs(data.Id, pushedFlag.Where(x => x == true).Count(), groups.Count));

事件放到构造函数，主要是新注入了一个scope工厂，这个也是关键代码，生成了的business和原来是不一样的。代码如下：

  public PushMessageController(IPushMessageBusiness pushMessageBusiness,
            IPushClientFactory factory,
            IEnumerable<ISpotBusiness> soptBusiness, IAutoPushMessageBusiness autoPushMessageBusiness,
            IServiceScopeFactory scopeFactory)
        {
            _pushMessageBusiness = pushMessageBusiness;
            _pushClient = factory.Create("ttttt");
            _soptBusiness = soptBusiness;
            _autoPushMessageBusiness = autoPushMessageBusiness;
            _scopeFactory = scopeFactory;
            SaveDataChangeEventEventHandler += (obj, args) =>
            {
                AsyncHelper.RunSync(async () =>
                {
                    using(var scope = _scopeFactory.CreateAsyncScope())
                    {
                        var _bus = scope.ServiceProvider.GetRequiredService<IPushMessageBusiness>();
                        var entity = await _bus.GetEntityAsync(x => x.Id.Equals(args.Id));
                        if (entity == null) { return; }
                        entity.SuccessCount = args.SucessCount;
                        entity.PushCount = args.PushCount;
                        await _bus.UpdateAsync(entity);
                    }
                  
                });

            };

        }
       
        private readonly IPushMessageBusiness _pushMessageBusiness;
        private readonly PushClient _pushClient;
        private readonly IEnumerable<ISpotBusiness> _soptBusiness;
        private readonly IAutoPushMessageBusiness _autoPushMessageBusiness;
        private record SaveDataChangeEventArgs(string Id, int SucessCount, int PushCount);    
        private EventHandler<SaveDataChangeEventArgs> SaveDataChangeEventEventHandler;
      
        private IServiceScopeFactory _scopeFactory;

 

 public static class AsyncHelper
    {
        private static readonly TaskFactory _myTaskFactory =
            new TaskFactory(CancellationToken.None, TaskCreationOptions.None, TaskContinuationOptions.None, TaskScheduler.Default);

        /// <summary>
        /// 同步执行
        /// </summary>
        /// <param name="func">任务</param>
        public static void RunSync(Func<Task> func)
        {
            _myTaskFactory.StartNew(func).Unwrap().ConfigureAwait(false).GetAwaiter().GetResult();
        }

        /// <summary>
        /// 同步执行
        /// </summary>
        /// <typeparam name="TResult">返回类型</typeparam>
        /// <param name="func">任务</param>
        /// <returns></returns>
        public static TResult RunSync<TResult>(Func<Task<TResult>> func)
        {
            return _myTaskFactory.StartNew(func).Unwrap().ConfigureAwait(false).GetAwaiter().GetResult();
        }
    }