An object-oriented and type-safe programming language that has its roots in the C family of languages and includes support for component-oriented programming.
1) There is an EF Core tag you can post to.
2) Transactions don't throw exceptions per say. There was another exception thrown that caused the the exception you have posted about most likely, which there may be an inner.excpetion.message if not null that could further explain the cause.
But I suggest that you post to the EF Core tag.