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I have been working with the Entity Framework + Self-Tracking entities, and came out with a problem:

Is there any way to determine when an entity has been changed??

For example: If you have an entity User with two fields: Name and Password, you can know if an User instance has been changed making:

<user>.ChangeTracker.State != ObjectState.Unchanged;

My problem is when the User has a Person, and the person has a field Email. I want that if the email field is changed, then the corresponding User is changed too.

I have been trying with methods such as: <user>.StartTrackingAll(); but this does not work with navigation properties (or maybe i am doing something wrong). Some help about this can be found here.

Remember that the Self tracking entities are autogenerated via T4 templates, so the clases can't be modified.

Ariel
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2 Answers2

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First when wanting to know if any entity in a so-called object graph has changed you can recurse through all entities contained in trackable collections or one-to-one navigation properties of a root entity (user in your case). This way you can know if a person inside the root entity has changed. This is actually how I check complex object graphs for any changes in any of the contained entities. But also for checking out if any of these entities have critical validation errors (so the user can't persist them yet).

Remember that the Self tracking entities are autogenerated via T4 templates, so the clases can't be modified.

Not true. First of all you can modify the T4 template to generate more (complex) code to achieve the things you want. And second, it generates partial classes which can easily be extended with custom (non-generated) code.

Youp Bernoulli
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  • that's true, but in a partial class you can't add any aditional behaviour for when a property changes. And i think this should be simple, altering the template to archieve this is too drastic (isn't it??). And as @LadislavMrnka says on it's answer, changing the STE behaviour could make them useless. – Ariel Jul 14 '11 at 05:20
  • @Ariel. Did you read the first part of my answer. This is the way I use it. Having a so-called WalkEntityGraphHandler which takes an (anonymous) delegate which checks if an entity has Changetracker.State other then Unchanged (so Modified, Added, Deleted). It's recursive and tells you if any entity in an object graph (as deep as you want) has been changed. – Youp Bernoulli Jul 14 '11 at 09:32
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If you change the email in the Person instance only that instance is correctly marked as modified. That is absolutely correct behaviour. What do you expect? Do you expect that change to property in related entity will propagate changed state to relations? That would make STEs completely useless because any single change to entity graph would make all entities in the graph modified and each this modification causes additional roundtrip to the database.

If you want to set User as modified when you are changing email simply create some method or handle some event and call person.User.MarkAsModified()

Ladislav Mrnka
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  • i don't want to mess with STE, just need a way to determinate when some property of the entity has been changed or not. To provide some kind of dirty check on the User entity, if it's person.email changes. – Ariel Jul 14 '11 at 05:14