When the ObservableCollection contains objects dervied from my DomainModel entity class, and I attempt to set a column filter value via the UI, the VS2008 Just In Time Debugger fires with the following error message:

 

"Cannot call BeginEdit() on Deleted or Detached entities".

 

In searching Infragistics forums, I came across this:

 

 

The Infragistics web grid control has an event called DataObjectRequested that is triggered when a blank row for filtering is required. However, I'm lost as to how to attach the "blank row" object to the existing Entity Manager. I'm using Prism & MVVM I don't want to couple the View to my ViewModel.

 

Any suggestions?

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Visual Studio Just-In-Time Debugger
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An unhandled exception ('Unhandled Error in Silverlight Application
Code: 4004   
Category: ManagedRuntimeError      
Message: System.InvalidOperationException: Cannot call BeginEdit() on Deleted or Detached entities
   at IdeaBlade.EntityModel.EntityWrapper.System.ComponentModel.IEditableObject.BeginEdit()
   at Infragistics.Silverlight.Controls.XamWebGrid.EnterEditModeInternal(Row row, Cell cell)
   at Infragistics.Silverlight.Controls.XamWebGrid.EnterEditMode(CellBase cell)
   at Infragistics.Silverlight.Controls.XamWebGrid.SetActiveCell(CellBase cell, CellAlignment alignment, InvokeAction action, Boolean allowSelection, Boolean

setFocus, Boolean scrollIntoView)
   at Infragistics.Silverlight.Controls.XamWebGrid.SetActiveCell(CellBase cell, CellAlignment alignment, InvokeAction action, Boolean allowSelection, Boolean

scrollIntoView)
   at Infragistics.Silverlight.Controls.XamWebGrid.SetActiveCell(CellBase cell, CellAlignment alignment, InvokeAction action, Boolean allowSelection)
   at Infragistics.Silverlight.Controls.Cell.OnCellMouseDown(MouseEventArgs e)
   at Infragistics.Silverlight.Controls.XamWebGrid.c(Object A_0, MouseButtonEventArgs A_1)
   at System.Windows.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
   at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, String eventName)    
') occurred in iexplore.exe [4980]. Just-In-Time debugging this exception failed with the following error: No installed debugger has Just-In-Time debugging

enabled. In Visual Studio, Just-In-Time debugging can be enabled from Tools/Options/Debugging/Just-In-Time.

Check the documentation index for 'Just-in-time debugging, errors' for more information.
---------------------------
OK  
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So, whenever something is about to go into edit mode, we check to see if the underlying data object implements IEditableObject. If it does, then we call the interface members. 

It appears that the  IdeaBlade.EntityModel.EntityWrapper doesn't like us calling the method on this object that represents the filter. 

Hard to say what they're exactly doing, however this isn't really something that we can handle on our end. 

Basically, for the filter row, we need a data object, so that we can filter, and display the correct editors for binding.  We do fire an event called DataObjectRequested, that allows you to override the object we use.  Perhaps you could provide an object that meets the criteria for the IdeaBlade object. 

-SteveZ

 

I did come up with a work around that solves this problem.

 

The Infragistics XamWebGrid needs a "blank" object that it uses to bind the filter row of the grid. In my case, I was binding a EntityObject to the grid for display purposes. When Infragistics creates the blank object, the filtering mechanism fails beacause the blank EntityObject is detached from an entity manager and can't go into an edit mode.

 

What I did was create another EntityManager in my view model, create a new EntityObject and added the EntityObject to that EntityManager. I then exposed the new EntityObject as a property (in my case, FilterRow) for the view model. In my XAML code behind, I then wired up the XamWebGrid.DataObjectReqested event to return the FilterRow property via the DataContext. The FilterRow object is used exclusively by the Infragistics filtering mechanism, so I don't have to worry about persisting the data. The only downside to this approach is that my view is now "aware" of my ViewModel since I had to wire up the DataObjectReqeusted event in my code behind.

 

At least for now, I have a functioning XamWebGrid with filtering capabilties.