【[转] EF cannot be tracked because another instance of this type with the same key is already being tracked】的更多相关文章

[转] EF cannot be tracked because another instance of this type with the same key is already being tracked

本文转自:http://stackoverflow.com/questions/6033638/an-object-with-the-same-key-already-exists-in-the-objectstatemanager-the-object cannot be tracked because another instance of this type with the same key is already being tracked If you load the entity…

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

这里记录一个在使用.net core中ef core执行数据库操作时遇到的问题: 我在代码中使用DbContext下的Update方法准备将更改后的数据像这样步到数据库: _context.Menus.Update(menu); 这是很常见的用法,但没想到一直报如下错误: The instance of entity type 'Menu' cannot be tracked because another instance with the same key value for {'Id'}…

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

一.问题描述 问题:The instance of entity type 'xxxx' 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 atta…

type parameters of <T>T cannot be determined; no unique maximal instance exists for type variable T with upper bounds int,java.lang.Object

今天在进行代码检查的时候出现下面的异常: type parameters of <T>T cannot be determined; no unique maximal instance exists for type variable T with upper bounds int,java.lang.Object 当时的第一感觉就是代码因为jdk版本太低引起的. 因为最后咨询了配置管理组的同事,确实发现是因为我本地jdk用的是1.7版本,而代码检查机器上用的是jdk1.6版本.因此出现了这…

EF 更新实体 The instance of entity type 'BabyEvent' cannot be tracked because another instance

加上AsNoTracking. 人不能两次踏入同一条河. 我 就踏入了.o(╥﹏╥)o…

The instance of entity type 'manager' 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 ent

最近在用ASP.NET CORE时遇到一些问题,现记录下: 出现上述错误,即在更新实体数据时出现的错误 services.AddDbContext<StoreContext>(c => c.UseInMemoryDatabase(Guid.NewGuid().ToString()).UseQueryTrackingBehavior(QueryTrackingBehavior.NoTracking));…

EF关于报错Self referencing loop detected with type的原因以及解决办法

1)具体报错 { "Message": "出现错误.", "ExceptionMessage": "“ObjectContent`1”类型未能序列化内容类型“application/json; charset=utf-8”的响应正文.", "ExceptionType": "System.InvalidOperationException", "StackTrace"…

EF 6.0 The conversion of a datetime2 data type to a datetime data type resulted in an out-of-range value. c#中的时间

在SQL server 中,有两种日期时间类型: 1.DateTime 它的范围是 1753-1-1 至 9999-12-31 2.DateTime2 它的满园是 0001-01-01 至 9999-12-31 EF实体框架给一个DateTime字段加载一个默认值是 {01/01/0001 00:00:00},它已经在SQL日期类型的范围之外了.所以,如果要让他正常工作,我们需要告诉EF框架不需要创建一个默认的日期时间值.我们可以在模型类型上加一个可空类型,表示它的值是可以为空的. [Displ…

使用Ef查询出现的问题The cast to value type 'System.Boolean' failed because the materialized value is null.的解决方法

把值类型的系统.布尔的失败是因为物化值是null.结果类型的泛型参数或查询必须使用可空类型. 解决方法: 请确保你查询中的字段值不为空或者做为空判断…

EF 5 最佳实践白皮书

Performance Considerations for Entity Framework 5 By David Obando, Eric Dettinger and others Published: April 2012 1. Introduction Object-Relational Mapping frameworks are a convenient way to provide an abstraction for data access in an object-orient…