Core data property not updating

With the help of Daria (see comment below) I have found a way to use Sqlite in-memory with multiple instances of the Db Context.Daria pointed out that the in-memory part is held in the Sqlite connection, so I create one options (which uses the Sqlite connection) and used that to create two separate Db Context instances – thanks Daria.

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The database diagram below shows the three tables, with the foreign key links from the Book Author linking table to the other two tables.

A linking table like this has foreign keys (FK in the diagram) which link to the primary key(s) (PK in the disgarm) of each end of the relationship – in this case the Book Id of the Book entity and the Author Id of the Author entity.

When Save Changes is called on line 24 it finds that the Author Links property of the book instance it loaded has changed.

Because this is a relationship it looks at the entities and finds that there is a new Book Author entity, which it adds to the database, and a author which is already in the database so it doesn’t have to add it.

– that means that EF Core will take a copy of the entities we read in so that it can spot any changes when you call Save Changes.

The listing below is one of my unit tests which adds the existing author “Martin Fowler” to the book called “Quantum Networking”, which currently has one author called “Future Person”.

To update a many-to-many relationship in the connected state: The disconnected state happens when the initial read of the data and update of the data are done separately, i.e.

they use different instances of the applications Db Context.

After the test has finished the book “Quantum Networking” has two authors, “Future Person” and “Martin Fowler” Note: The default way of loading data in EF Core is as tracked entities, that is, EF Core takes a copy of the loaded data so that it can detect if any changes have happened since they were loaded.

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