Entity Framework doesn't delete children, instead sets references to null - entity-framework

Question

I have the following situation:
First the only relevant table/class (all auto generated from DB (MySQL)):
The relevant part of the edmx file:
<Association Name="navigationitem_ibfk_1">
<End Role="navigationitem" Type="Model.Store.navigationitem" Multiplicity="0..1">
<OnDelete Action="Cascade" />
</End>
<End Role="navigationitem1" Type="Model.Store.navigationitem" Multiplicity="*" />
<ReferentialConstraint>
<Principal Role="navigationitem">
<PropertyRef Name="id" />
</Principal>
<Dependent Role="navigationitem1">
<PropertyRef Name="navigationitemid" />
</Dependent>
</ReferentialConstraint>
</Association>
I think there aren't many more words needed: It's a navigation table, each navigationitem can have children (but it's not a must).
Now when I try to remove a top level item which has a child:
context.Remove(topLevelNode);
context.SaveChanges();
It deletes the top level node in the DB, but at the child nodes it just sets the navigationitemid to null (and yes - I have defined on delete cascade in the DB, when I delete it directly there it works).
So what I think it's going on is, that when I delete the parent node, the framework sets all navigationitemid of all children to NULL, then when the navigation should be saved to the DB it won't cascade the delete because the navigationitemid of the children are NULL.
What can I do? Thank you.

Answer 1

The obvious thing one would like to do is define cascade deletes on the association in the context. But trying it I found out that either sql server does not support it or EF needs help:
Defining cascade delete on the foreign key constraint (using code-first) throws a sql server exception:
Introducing FOREIGN KEY constraint 'xxx' on table 'yyy' may cause cycles or multiple cascade paths. (See here.)
Cascade delete in EF model: now when deleting a parent the child records are not deleted. Even worse: the FK fields are not nullified and the foreign key constraint violation will throw an exception. The remedy is to load the child collection before deleting the parent.
Especially when deleting a tree of navigationitems this is not a very attractive option, but I'm afraid it's all you've got at the moment.