Update data without select it first

[JC Wu]

We can update a row by these code.
          var application = context.Applications.Single(app=> app.App_code == "123");
          application.App_name = "test";
          context.SaveChanges();

In microsoft entity framework, we can use Attach to do this update without select first.
         var application = new Applications();
         application.App_Code = "123";
         context.Applications.Attach(application);
         application.App_name = "test";
         context.SubmitChanges();

How can I do this in telerik ORM?

[Viktor Zhivkov]

Hi JC Wu,

In order to update an existing entity you need to load it in memory first.
This can be achieved using various operations like the first LINQ query that you have posted.
OpenAccess does not allow creation of new entity instances and using them to update existing one.
If you want to mark one to be updated via the Attach mechanism you will have to detach the same entity first. 
For more information about our attach-detach functionality please see this online article.

If you have any further questions, do not hesitate to contact us again.

Kind regards,
Viktor Zhivkov
the Telerik team

[JC Wu]

Thanks for reply.
In the online article, when detach

public void DetachObjectGraph(EntitiesModel dbContext)
{
Car carToDetach = dbContext.Cars.FirstOrDefault();
Car detachedCopy = dbContext.CreateDetachedCopy(carToDetach, car => car.Category, car => car.RentalOrders);
}

So it's necessary to get entity first?

[Boris Georgiev]

Hello, 

Yes, is necessarily to have loaded in the cache the entity that you want to detach from the context. By design OpenAccess uses the entity for the root of the graph which will be detached from the current context - that is why needs to be loaded.

Note that only the primary key values are loaded for an object by default (with FirstOrDefault()), so CreateDetachedCopy method will also internally retrieve any persistent fields from the database that are not cached yet.

I hope that helps. Do not hesitate to contact as again if you have any other questions.

Kind regards,
Boris Georgiev
the Telerik team

[JC Wu]

Got it, thanks.