EFCoreRelatedEntityDeletePOC

I'm going to keep things short and simple. This is a proof of concept demo solution for a potential Entity Framework Core (2.2 & 3.1) I stumbled upon.

Running the demo

load in your favorite IDE
restore packages
build solution
open up DemoDbContext and change the connection string to the SQL database you want to use
depending on which version you want to test, run the corresponding migration to set up the database
run

Context

Let's say we have 3 classes: A,B,C (named like this).

A and C both contains a B instance.

Since this is a code first example the generated db will have 3 tables As, Bs, Cs with As and Cs having a nullable foreing key to Bs.

And let's say this setup is used in a web app and we want to update an A and a C which both have a B and remove those B(s) from them.

Expected behavior

I would expect that once I detected that a delete of B happened on either A or C and I applied the update (removing the foreign key value) of A/C and the delete of B on the EF context, when I call SaveChanges EF generates the correct SQL commands in the correct order.

Observed behavior

In reality for the A case it works, for the C case it doesn't. Apparently, form what I was able to make out, the statements are generated in the alphabetical order of the affected tables of the tracked entities. Until now I was certain that EF checks the dependencies of the tracked entities in order to apply the changes in the expected sequence, so I find this a bit baffling.

EF6 example