Perseus: Entity Framework EntityBag

UPDATED WIKI: Home

Danny — Thu, 05 Nov 2009 18:38:04 GMT

Perseus is a small project designed to explore ways for exchanging graphs of Entity Framework entities over WCF web services. The key piece of the project is EntityBag<T> which stores a graph of entities along with change tracking information. Here's hoping no one will use this to store & transport something as nasty as Medusa's head. ;-)

This project is no longer being maintained.

It's still here as an example of how to do some things with the EF, but the functionality has been subsumed by Self-Tracking Entities in EF4. For more information see this blog post:

http://blogs.msdn.com/dsimmons/archive/2009/11/05/it-s-time-to-rip-up-entitybag-and-throw-it-away.aspx

Archive:

For more information about this project and a walk through of the code, take a look at these blog posts:

EntityBag Series

Extension Methods Series

Original Values Entities and Graphs

NEW POST: Any one got this working ?

Moonshield — Mon, 26 Oct 2009 19:27:54 GMT

I have the same problem, the library works well for updating data, but I am not able to insert a new record.
I'm also trying to get it working, did you find any solutions ?

NEW POST: Perseus and Silverlight

TimmyC — Sat, 24 Oct 2009 16:13:37 GMT

Hello!

This is a nicely convenient implementation of what is really needed - graph updates on Entity Data Models, but I am unable so far to get this working with Silverlight. I have the service set up and it seems to work as expected, but upon succesfully rebuilding the service reference from my Silverlight application, the result of my "Get" query is not EntityBag<Universe> but instead EntityBagOfUniverseVbzhej4. This object has no Root property, and so I have troubles. I am, of course, unable to reference the Perseus project in Silverlight.

Any guidence on what to do from here?

Thank you!

Tim

NEW POST: Any one got this working ?

mrunalbuch — Thu, 20 Aug 2009 13:56:35 GMT

Hi,

I am trying to implement the entitybag in one of my projects and I am not able to Insert/Update the records as suggested by your code snippet.

foreach (IEntityWithKey entity in this.unchangedEntities)
{
context.Attach(entity);
}

The above code gives me following exception

"An object with a temporary EntityKey value cannot be attached to an object context."

I am able to retrieve the record though. Please please help me with this. Hope someone answers this post as there are lot of unanswered posts.

NEW POST: Problem building v 1.1

imtiz_ahmed — Fri, 20 Feb 2009 12:47:35 GMT

I've downloaded and tried to build the version 1.1 and got a bunch of errors (most of then in Northwind project). Can anybody tell what could be the problem? I am using VS 08 SP1.

NEW POST: Cannot build Perseus

AndreyTS — Fri, 31 Oct 2008 02:32:06 GMT

Thanks very much! That works for me, too.

NEW POST: Cannot build Perseus

girolo — Fri, 10 Oct 2008 16:21:18 GMT

Solution FOUND !

Replace : context.GetEntityKey(fullEntitySetName, target)

By

EntityKey targetKey;
EntityObject e = target as EntityObject;
if (e != null && e.EntityKey != null)
{
targetKey = e.EntityKey;
}
else
{
targetKey = context.CreateEntityKey(fullEntitySetName, target);
}

Now it works on VS2008 SP1

NEW POST: Cannot build Perseus

girolo — Fri, 10 Oct 2008 12:59:00 GMT

Hello,
For me, replacing GetEntityKey(fullEntitySetName, target);
by CreateEntityKey(fullEntitySetName, target);
did not seems to work because when I try to persist modifications I got an InvalidOperationException exception
The supplied EntityKey does not have a corresponding entry in the ObjectStateManager.
in the line just after :
EntityKey targetKey = context.CreateEntityKey(fullEntitySetName, target);
ObjectStateEntry targetStateEntry = context.ObjectStateManager.GetObjectStateEntry(targetKey); <---- Exception

Any idea ?
Thanks for your help.

NEW POST: Cannot build Perseus

allexey — Fri, 13 Jun 2008 11:55:58 GMT

Great. It works. At least I succeeded in launching it and getting bag from service :)

NEW POST: Cannot build Perseus

allexey — Thu, 12 Jun 2008 16:34:41 GMT

Hi everyone.
I've downloaded both 1.0 and 1.1 versions and I can't buid any of them.
Studio cannot find extension method GetEntityKey in this row:

EntityKey targetKey = context.GetEntityKey(fullEntitySetName, target);

there exists method with such name but it has different parameters list & interface it applies to. I could not find any method that would have such a signature.

Did anyone succeeded in using Perseus?

NEW POST: Is this project still active?

papadi — Fri, 06 Jun 2008 15:00:00 GMT

Hi,
is this project still active?

NEW POST: Change reference on one to one object?

martintr — Tue, 12 Feb 2008 06:45:29 GMT

HI Danny
Sorry to be a pest but I am trying to change references and nothing I try succeeds.
I can use SetEntityKey(null) to set the existing key to null before trying to assign another one
but it seems to not like the context of reattaching a new key.

Any help would be greatfully accepted at this point as it is gettng frustrating.

Thanks
MartinT

NEW POST: Use of entitybag in real application?

martintr — Mon, 11 Feb 2008 00:20:38 GMT

Hi Danny
I am interested in using Perseus in a real application using WCF Services and Entity Framework.
Would this be a realistic path to follow as I have not yet seen a reliable way to do updates of disconnected Entities using Entity Framework.

Is EntityBag likely to become the standard for doing this sort of work?

I really like what you have done with this application and will likely take it further for my own use.
Would be interested in any comments you may feel to pass on.

Thanks
Martin

UPDATED WIKI: Home

Danny — Mon, 28 Jan 2008 10:52:59 GMT

Extension Methods Series

Original Values Entities and Graphs

RELEASED: Perseus 1.1 (Jan 27, 2008)

Mon, 28 Jan 2008 10:52:22 GMT

* Fixes a bug in Perseus 1.0 with connection strings that use name to look up values from the config file.
* Adds a full working sample service.

See [url:http://blogs.msdn.com/dsimmons/archive/2008/01/28/entitybag-wrap-up-and-future-directions.aspx] for more info.

UPDATED RELEASE: Perseus 1.1 (Jan 27, 2008)

Mon, 28 Jan 2008 10:52:22 GMT

UPDATED WIKI: Home

Danny — Thu, 24 Jan 2008 22:57:19 GMT

Extension Methods Series

Original Values Entities and Graphs

UPDATED WIKI: Home

Danny — Thu, 24 Jan 2008 00:47:36 GMT

Extension Methods Series

Original Values Entities and Graphs

UPDATED WIKI: Home

Danny — Thu, 24 Jan 2008 00:44:19 GMT

Extension Methods Series

Original Values Entities and Graphs

UPDATED WIKI: Home

Danny — Wed, 23 Jan 2008 08:54:15 GMT

Resource Page Description
Perseus is a small project designed to explore ways for exchanging graphs of Entity Framework entities over WCF web services. The key piece of the project is EntityBag<T> which stores a graph of entities along with change tracking information. Here's hoping no one will use this to store & transport something as nasty as Medusa's head. ;-)

For more information about this project and a walk through of the code, take a look at these blog posts:

EntityBag Series

Extension Methods Series

Original Values Entities and Graphs