ASP。附加一个“MODELNAME”类型的实体失败，因为另一个相同类型的实体已经具有相同的主键值

In a nutshell the exception is thrown during POSTing wrapper model and changing the state of one entry to 'Modified'. Before changing the state, the state is set to 'Detached' but calling Attach() does throw the same error. I'm using EF6.In a nutshell the exception is thrown during PO