DevForce 2010: Null Entity Incorrectly Attached

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Null Entity Incorrectly Attached

Printed From: IdeaBlade
Category: DevForce
Forum Name: DevForce 2010
Forum Discription: For .NET 4.0
URL: http://www.ideablade.com/forum/forum_posts.asp?TID=2929
Printed Date: 13-May-2026 at 9:25pm

Topic: Null Entity Incorrectly Attached

Posted By: Didsbo
Subject: Null Entity Incorrectly Attached
Date Posted: 26-Aug-2011 at 1:53am

Hi,

I'm experiencing unexpected behaviour in my silverlight application. When I add an entity of type Order to the entity manager using EntityManager.AddEntity(order), an entity is also added to the entity manager for the Customer navigation property (order.Customer). The customer entity is effectively a null entity (Id is an empty Guid) however customer.EntityAspect.IsNullEntity is false. The customer null entity should not be added to the manager and should remain detached.

In my WPF application, using the the same entitymodel, the customer null entity is correctly never added to the entitymanager and remains detached when I add an order.

Is this behaviour for Silverlight expected? Why is it different to the WPF behaviour? What can I do to prevent null entities being added to the EntityManager?

Thanks

Ian

Replies:

Posted By: Didsbo
Date Posted: 26-Aug-2011 at 2:08am

Interestingly, if I query EntityManager.Customers before I create and add an order then the customer null entity is correctly not added to the entitymanager. Wierd.

Posted By: sbelini
Date Posted: 29-Aug-2011 at 11:28am

Hi Didsbo,

I was not able to reproduce the behavior you described.

var mgr = new NorthwindIBEntities();

var order = new Order();mgr.AddEntity(order);

var customerEntityState = order.Customer.EntityAspect.EntityState; // customerEntityState is Detached

var isNullCustomer = order.Customer.EntityAspect.IsNullEntity; // isNullCustomer is true

Can you provide a sample reproducing the issue? (against NorthwindIB, please)

Regards,

Silvio.

Posted By: Didsbo
Date Posted: 31-Aug-2011 at 4:57am

Hi Silvio,

Thanks for the reply. I'll create a sample using Northwind as requested however in the meantime the following information relating to my model might be useful.

I have an entity call Asset that has a 1 to many association with an entity call SystemItem. The SystemItem entity has a recursive (0..1 to many) associated (Parent/ Children).

If I create a SystemItem as follows I can reproduce the behaviour in my Siverlight application but not in my WPF application (identical model):

var mgr = new MyEntities();

var systemItem= new SystemItem();

systemItem.Id = Guid.NewGuid()

var assetEntityState = systemItem.Asset.EntityAspect.EntityState; // assetEntityState is Detached

var isNullAsset = systemItem.Asset.EntityAspect.IsNullEntity; // isNullCustomer is false

var parentEntityState = systemItem.Parent.EntityAspect.EntityState; // assetEntityState is Detached

var isNullParent = systemItem.Parent.EntityAspect.IsNullEntity; // isNullCustomer is false

mgr.AddEntity(systemItem);

var assetEntityState = systemItem.Asset.EntityAspect.EntityState; // assetEntityState is Attached

var isNullAsset = systemItem.Asset.EntityAspect.IsNullEntity; // isNullCustomer is True

var parentEntityState = systemItem.Parent.EntityAspect.EntityState; // assetEntityState is Detached

var isNullParent = systemItem.Parent.EntityAspect.IsNullEntity; // isNullCustomer is false

I have resolved this issue by quering mgr.Assets (local cache only) before creating a SystemItem. In fact, I don't have to query Assets as any query against the EntityManager will resolve the issue. It seems this issue might be related to the initialisation of the EntityManager. This issue effects all entities in model, not just Assets and SystemItems, where the multiplicity is 1.

If you can't reproduce using NorthwindIB then the problem must be with my model. I can't think where the problem might be. Any ideas?

I thought it might be related by my SystemItem buddy class / metadata - a have a NullValueVerifier attribute on the Asset property. I removed this but still had the issue.

Regards

Ian

Posted By: sbelini
Date Posted: 31-Aug-2011 at 7:44am

Hi Ian,

Thanks for the clarification.

I'll try to repro it here and let you know.

Silvio.

Posted By: sbelini
Date Posted: 31-Aug-2011 at 10:39am

Ian,

It looks like I will need a reproducible solution from you as I could not repro it here.

I've used Orders *_0..1 Employee and Employee1 *_0..1 Employee2 from NorthwindIB to test:

var mgr = new NorthwindIBEntities();

var employee = new Employee();

mgr.AddEntity(employee);

var employee2EntityState = employee.Employee2.EntityAspect.EntityState; // employee2EntityState is Detached

var isNullEmployee2 = employee.Employee2.EntityAspect.IsNullEntity; // isNullEmployee2 is true

mgr.Clear();

var order = new Order();

mgr.AddEntity(order);

var employeeEntityState = order.Employee.EntityAspect.EntityState; // employeeEntityState is Detached

var isNullEmployee = order.Employee.EntityAspect.IsNullEntity; // isNullEmployee is true

Regards,

Silvio.

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