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MCCB ObservableCollection exceptions

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MultiColumnComboBox
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Ian
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Ian asked on 05 Feb 2019, 04:44 PM

Hi, I am having an issue with a standalone RadMultiColumnComboBox.  It needs to be populated differently each time I select a different entity (User) from a RadGridView.  As I understand it the only way to do this is with events. 

The problem is that I run into an exception when I try to clear the selected items from the MCCB (basically, I need to reset it), and add the new selections.  I get various ObservableCollection changed event exceptions.  

What is the correct way to do this to avoid these type of exceptions? 

Thanks,

Ian

 

Here is the code I use so far: 

 

Private changingUser As Boolean = False
 
Private Sub RadMultiColumnComboBox_SelectionChanged(sender As Object, e As SelectionChangeEventArgs)
    Try
        SyncLock lockObject
            If changingUser Then
                e.Handled = True
                changingUser = False
                Exit Sub
            End If
        End SyncLock
 
        If e.AddedItems.Count = 0 AndAlso e.RemovedItems.Count = 0 Then Exit Sub
        vm.AddRemoveRoles(e.AddedItems, e.RemovedItems)
    Catch ex As Exception
    Finally
        e.Handled = True
    End Try
End Sub
 
Private Sub Grid_SelectionChanged(sender As Object, e As SelectionChangeEventArgs)
    Try
        SyncLock lockObject
            changingUser = True
        End SyncLock
        RolesBox.SelectedItems.SuspendNotifications() 'RolesBox is the RadMultiColumnComboBox
        RolesBox.SelectedItems.Clear()
        Dim roles = vm.GetSelectedUserRoles
        For Each r In roles
            RolesBox.SelectedItems.Add(r)
        Next
    Catch ex As Exception
    Finally
        RolesBox.SelectedItems.ResumeNotifications()
 
        SyncLock lockObject
            changingUser = False
        End SyncLock
 
    End Try
 
End Sub

 

Here is an example of the exceptions I am getting: 

System.InvalidOperationException: 'Cannot change ObservableCollection during a CollectionChanged event.'

   at System.Collections.ObjectModel.ObservableCollection`1.CheckReentrancy()
   at System.Collections.ObjectModel.ObservableCollection`1.RemoveItem(Int32 index)
   at System.Collections.ObjectModel.Collection`1.Remove(T item)
   at Telerik.Windows.Controls.RadMultiColumnComboBox.OnSelectedItemPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs args)
   at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
   at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
   at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
   at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
   at System.Windows.DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType, Boolean isInternal)
   at System.Windows.DependencyObject.SetValue(DependencyProperty dp, Object value)
   at Telerik.Windows.Controls.MultiColumnComboBox.SelectionBridge.ItemsSelectedInOwner(IEnumerable`1 addedItems)
   at Telerik.Windows.Controls.MultiColumnComboBox.SelectionBridge.OwnerSelectedItemsCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item)

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Dinko
Telerik team
answered on 07 Feb 2019, 02:48 PM
Hello Ian,

Thank you for the provided code snippets. 

If I have understood your scenario correctly, you have separate RadGridView and RadMultiColumnComboBox and you are trying to sync their selected items. I have double check this on my side but wasn't able to reproduce this exception. The project is attached to this reply. May I ask you to take a closer look and let me what I need to modify to reproduce this exception.

Regards,
Dinko
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Dinko
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