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 attached.

二、解决方案

　　就是把插入的主键自动赋值即可 id=SequentialGuidGenerator.Instance.Create();

三、示例