Description
GraphDiff can handle associated entities, when updating an entity graph then associated entities are not changed by GraphDiff.
- The child entity is not a part of the aggregate. The parent's navigation property will be updated, but changes to the child will not be saved.
- Only the relation is added, but any changes made to the associated entity will not be updated.
- Associated entity or a collection of associated entities must be specified in the AssociatedEntity() or AssociatedCollection() method respectively.
Add Associated Entity
GraphDiff adds the relation of an associated entity to the parent entity when entity graph is updated.
var node = new TestNode { Title = "Parent Node" }; using (var context = new TestDbContext()) { context.Nodes.Add(node); context.SaveChanges(); } // Simulate detach node.OneToOneAssociated = new OneToOneAssociatedModel { Title = "Associated Entity" }; using (var context = new TestDbContext()) { // Setup mapping context.UpdateGraph(node, map => map .AssociatedEntity(p => p.OneToOneAssociated)); context.SaveChanges(); }
Similarly, the relation of a collection of associated entities can also be added to the parent entity by using the AssociatedCollection() method.
var node = new TestNode { Title = "Parent Node" }; using (var context = new TestDbContext()) { context.Nodes.Add(node); context.SaveChanges(); } // Simulate detach node.OneToManyAssociated = new List<OneToManyAssociatedModel> { new OneToManyAssociatedModel { Title = "Associated Entity 1" }, new OneToManyAssociatedModel { Title = "Associated Entity 2" }, new OneToManyAssociatedModel { Title = "Associated Entity 3" } }; using (var context = new TestDbContext()) { // Setup mapping context.UpdateGraph(node, map => map .AssociatedCollection(p => p.OneToManyAssociated)); context.SaveChanges(); }
If the associated collection has many navigation properties with the same parent entity, such as:
public class Child { public Parent A { get; set; } public Parent B { get; set; } public Parent Inverse { get; set; } }
You can choose which navigation to use; otherwise, the first one found will be used (in this case A).
context.UpdateGraph(entity, map => map.AssociatedCollection(c => c.Children, x => x.B)
Change Associated Entity
Any change in an associated entity will not be saved with parent's navigation property.
var node = new TestNode { Title = "Parent Node", OneToOneAssociated = new OneToOneAssociatedModel { Title = "Associated Entity" } }; using (var context = new TestDbContext()) { context.Nodes.Add(node); context.SaveChanges(); } // Simulate detach node.OneToOneAssociated.Title = "Updated Associated Entity"; using (var context = new TestDbContext()) { // Setup mapping context.UpdateGraph(node, map => map .AssociatedEntity(p => p.OneToOneAssociated)); context.SaveChanges(); }
In the above example, the Title of associated entity is updated, but GraphDiff will not save the updated Title when entity graph is updated.