There is a
discussion about WCR RIA Services and how to update an EntitySet after a Submit
changes, on the Silverlight forum. If we loads a set of entities they will be
cached in an EntitySet on the client-side, so
after a Submitting changes only
the entities we have removed on the client will be removed from the
client-side’s EntitySet. If someone else have removed some of the entities from
the database we work against, we still have those cached on the client-side. At
the moment there aren’t any reload features added to the WCF RIA Services, so
we need to handle it by our self. We can’t just make a new call to the Load
method of our DomainContext, it will only “merge” the existing EntitySet with
changes or add new entities, but not removing anything. So what we need to do,
is to implement code which will handle the removing of entites from the
EntitySet. Here is an example code which will make sure removed entities
(entities which is cached since an early Load operation but not part of the new
Load operation) will be removed from the cached EntitySet:
_domainContext.SubmitChanges(
submitOperation =>
{
_domainContext.Load<Customer>(
_domainContext.GetCustomersQuery(),
LoadBehavior.RefreshCurrent,
loadOperation =>
{
var results =
_domainContext.Customers.Where(
entity =>
!loadOperation.Entities.Contains(entity)).ToList();
results.ForEach( enitity =>
_domainContext.Customers.Detach(entity));
}, null);
}, null);
The above code will
after a SubmitChanges Load new entities from the server. The LoadBehavior is
set to RefreshCurrent, it will make sure to refresh the current entities in the
cached EntitySet, but will not remove anything. When the Load operation is completed
and we got the new entities from the server, we then need to get the entities
which is not part of the last Loading from the cached EnitySet:
var results =
_domainContext.Customers.Where(
entity =>
!loadOperation.Entities.Contains(entity)).ToList();
Then we need to
Detach the entities from the EntitySet. We can’t use the Remove method of the
EntitySet, it will only mark entities for deletion. But the Detach method will
not mark them and just remove them form the EntityList.
results.ForEach(
enitity => _domainContext.Customers.Detach(entity));
We could also just
clear the EntitySet buy setting using its Clear method before calling the Load
method, but if we have bound the EntitySet to a data-bound control,the control
will be notified when the EntitySet is cleared. That will make it “blink”. With
the above solution there will not be any blinking.
I will not take all
the credits for the solution in this blog post, I will thank Colin Blair for
the basic ideas of removing entities from the EntitySet. In the future I hope
we will se some other solution with less efforts.
If you want to know
when I publish a new blog post, you can follow me on twitter: http://www.twitter.com/fredrikn
Published Tuesday, November 24, 2009 7:35 PM
by Fredrik N
Inserted
from <http://weblogs.asp.net/a/Banner.htm>
