This is what is currently happening

In OrderGrid Row update method

1) I set a flag let's say updatingDB = true

2) I call entity manager to save changes on the new row

3) On callback of save I set updating DB = false

In the invoice save I do

1) Check updatingDB

2) if true then sleep and loop to check again 

3) Update invoice

The problem is that while it is executing the loop to check the updatingDB flag the callback for the order row save is never processed.

I tried moving the check to a background thread but then the entity manager save for the invoice complained that it had to be executed on the UI thread.

Background:

I have a foreign key relationship lets say invoice and orders.  On the invoice screen I have a grid to maintain the orders using in place editing.  If I enter an order and then click the save invoice button what happens is the following

1) The row change occurs and it tries to commit the currently edited order to the database asynchronously

2) It tries to save the invoice and its orders.  When I save an invoice I get an entity graph of related objects and call the savechangesasync with this list.

3) I get the callback from the order save

4) I get the callback from the invoice save

As far as I can tell this is a concurrency issue.  Basically at the time of saving both items have key of -100 so they both do an insert into the table.  Is there a way of blocking the second save until the first save is done?  The saving is happening in a separate sandbox so I'm happy to make saves  "single-threaded" within that entity manager.