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Force Refresh of Navigation Properties

Printed From: IdeaBlade
Category: DevForce
Forum Name: DevForce 2009
Forum Discription: For .NET 3.5
URL: http://www.ideablade.com/forum/forum_posts.asp?TID=1468
Printed Date: 22-Sep-2025 at 1:01am


Topic: Force Refresh of Navigation Properties
Posted By: ken.nelson
Subject: Force Refresh of Navigation Properties
Date Posted: 11-Sep-2009 at 1:28pm
Hi,
 
Is there any way to force a refresh/refetch of a navigation property?  I've tried a few things, and the most promising appeared to be something along the lines of customer.Orders.Reload(MergeStrategy.OverwriteChanges), but it didn't appear to work.
 
I worked around it by removing the entity from the entity manager, then requerying for the same entity, but that seems less than ideal.  Is there a better way of doing this?
 
Thanks,
Ken


Replies:
Posted By: GregD
Date Posted: 14-Sep-2009 at 2:46pm
Reload() should do it, and it seems to work for me.  I tested it as follows in a console app against NorthwindIB:

    private void DoIt() {
      Order anOrder = _mgr.Orders.FirstOrDefault();
      Console.WriteLine("Order Id = {0}; No. of OrderDetails = {1}", anOrder.OrderID, anOrder.OrderDetails.ToList().Count());
      Console.WriteLine("Pause here and add an OrderDetail to this outside of this program...");
      PromptToContinue();
      anOrder.OrderDetails.Reload(MergeStrategy.PreserveChanges);
      Console.WriteLine("Order Id = {0}; No. of OrderDetails = {1}", anOrder.OrderID, anOrder.OrderDetails.ToList().Count());
      PromptToContinue();
    }

    private void PromptToContinue() {
      Console.WriteLine();
      Console.WriteLine("Press ENTER to continue...");
      Console.ReadLine();
    }

At the first PromptToContinue(), while execution was paused, I manually changed the OrderId in one or more of the records in the OrderDetail backing table, in such a way as either to add or remove an OrderDetail from the OrderDetails collection of anOrder. The second output of the OrderDetails count shows the change. I tested it both for an increased and a decreased collection, thinking that maybe it only reloaded entities it already had, but it does pick up newly added children as well.

Of course, the way Reload handles externally made changes to an entity that's already in the collection depends upon the MergeStrategy you use. If you use PreserveChanges, for example, then in the case of an entity that has changed both in the cache and externally, you would not pick up the external changes.

Posted By: ken.nelson
Date Posted: 15-Sep-2009 at 6:47am
The merge strategy we're using is OverwriteChanges, so that shouldn't be the problem. 
 
I can't speak for a win form console application version because I didn't test that.  Is it possible that this feature works in syncronous win forms but not in asynchronous Silverlight apps?  Truthfully I was a bit surprised there wasn't a ReloadAsync() method.
 

Posted By: GregD
Date Posted: 15-Sep-2009 at 10:21am
Originally posted by ken.nelson

Is it possible that this feature works in syncronous win forms but not in asynchronous Silverlight apps?  Truthfully I was a bit surprised there wasn't a ReloadAsync() method.


Oh, sorry, I wasn't paying attention to which forum we're in.  Of course it would need to be async. Perhaps we've simply not implemented that yet, in which case you'd just have to do a normal async query to refresh the related entities. I'll check into it.

Posted By: GregD
Date Posted: 15-Sep-2009 at 2:04pm
Ken:

I haven't tested this, but I'm told that Reload does work in SL, the same as the usual (implicit) load of related entities – it will be performed asynchronously if the UseAsyncNavigation flag is true on the EntityManager, which it will be for a SL app.  This means that you will either need to have a handler in place for PendingEntityListResolved, or check the IsPendingEntityList flag, to determine when the list is reloaded.

Greg


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