How to remove all views in region in CompositeWPF/Silverlight

Question

Hi.

I want remove all views from my region in Composite. I'm using Silverlight 4.0.

And unfortunately, this code crashes with OutOfRangeException inside Composite.

        List<object> views = new List<object>(_regionManager.Regions["NavigationRegion"].Views);

        foreach (object view in views)
        {
            _regionManager.Regions["NavigationRegion"].Remove(view);
        }

This is my callstack:

[External Code] Microsoft.Practices.Composite.Presentation!Microsoft.Practices.Composite.Presentation.Regions.ViewsCollection.OnCollectionChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e = {System.Collections.Specialized.NotifyCollectionChangedEventArgs}) Line 102 + 0x24 bytes C# Microsoft.Practices.Composite.Presentation!Microsoft.Practices.Composite.Presentation.Regions.ViewsCollection.RemoveAndNotify(System.Collections.IList items = Count = 1) Line 45 + 0x2b bytes C# Microsoft.Practices.Composite.Presentation!Microsoft.Practices.Composite.Presentation.Regions.ViewsCollection.UnderlyingCollection_CollectionChanged(object sender = Count = 0, System.Collections.Specialized.NotifyCollectionChangedEventArgs e = {System.Collections.Specialized.NotifyCollectionChangedEventArgs}) Line 153 + 0xb bytes C# [External Code] Microsoft.Practices.Composite.Presentation!Microsoft.Practices.Composite.Presentation.Regions.Region.Remove(object view = {Kite.MyApp.SlUI.NavigationRegion.NavigationRegionView}) Line 230 + 0x1b bytes C# MyApp.SlUI!Kite.MyApp.SlUI.Components.ViewController.linksRegion_LanguageChanged(object sender = {Kite.MyApp.SlUI.Controls.LinksUserControl}, Kite.MyApp.SlUI.Common.EventArgs e = {Kite.MyApp.SlUI.Common.EventArgs}) Line 77 + 0x2d bytes C# MyApp.SlUI!Kite.MyApp.SlUI.Controls.LinksUserControl.OnLanguageChanged(string newLanguage = "en-GB") Line 37 + 0x32 bytes C# MyApp.SlUI!Kite.MyApp.SlUI.Controls.LinksUserControl.ComboBox_SelectionChanged(object sender = {System.Windows.Controls.ComboBox}, System.Windows.Controls.SelectionChangedEventArgs e = {System.Windows.Controls.SelectionChangedEventArgs}) Line 31 + 0xb bytes C# [External Code]

What did I wrong?

P.S. In my region I have 3 views. So, composite crashes on removing the third.

Hoping for you help :). Thank you.

UPD: I downloaded debug symbols and found that problem is only in Accordion control as region. This is full call stack:

mscorlib.dll!System.ThrowHelper.ThrowArgumentOutOfRangeException(System.ExceptionArgument argument, System.ExceptionResource resource) + 0x41 bytes 
mscorlib.dll!System.ThrowHelper.ThrowArgumentOutOfRangeException() + 0x10 bytes 
mscorlib.dll!System.Collections.Generic.List<object>.this[int].get(int index = 0) + 0x13 bytes  
System.Windows.dll!System.Windows.Controls.ItemCollection.GetItemImpl(int index) + 0x15 bytes   
System.Windows.dll!System.Windows.Controls.ItemCollection.GetItemImplSkipMethodPack(int index) + 0xb bytes  
System.Windows.dll!System.Windows.PresentationFrameworkCollection<System.__Canon>.this[int].get(int index) + 0xb bytes  
System.Windows.Controls.Layout.Toolkit!System.Windows.Controls.Accordion.UnselectItem(int index = 0, object item = null) + 0x1aa bytes  
System.Windows.Controls.Layout.Toolkit!System.Windows.Controls.Accordion.ChangeSelectedIndex(int oldIndex = 0, int newIndex = -1) + 0x14c bytes 
System.Windows.Controls.Layout.Toolkit!System.Windows.Controls.Accordion.OnSelectedIndexPropertyChanged(System.Windows.DependencyObject d = {System.Windows.Controls.Accordion}, System.Windows.DependencyPropertyChangedEventArgs e = {System.Windows.DependencyPropertyChangedEventArgs}) + 0x1d9 bytes   
System.Windows.dll!System.Windows.DependencyObject.RaisePropertyChangeNotifications(System.Windows.DependencyProperty dp = {System.Windows.CustomDependencyProperty}, object oldValue, object newValue) + 0x51 bytes    
System.Windows.dll!System.Windows.DependencyObject.UpdateEffectiveValue(System.Windows.DependencyProperty property, System.Windows.EffectiveValueEntry oldEntry, ref System.Windows.EffectiveValueEntry newEntry, System.Windows.DependencyObject.ValueOperation operation) + 0xf5 bytes    
System.Windows.dll!System.Windows.DependencyObject.SetValueInternal(System.Windows.DependencyProperty dp, object value, bool allowReadOnlySet) + 0x2ad bytes    
System.Windows.dll!System.Windows.DependencyObject.SetValue(System.Windows.DependencyProperty dp, object value) + 0xb bytes 
System.Windows.Controls.Layout.Toolkit!System.Windows.Controls.Accordion.SelectedIndex.set(int value = -1) + 0x4d bytes 
System.Windows.Controls.Layout.Toolkit!System.Windows.Controls.Accordion.OnItemsChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e = {System.Collections.Specialized.NotifyCollectionChangedEventArgs}) + 0x737 bytes    
System.Windows.dll!System.Windows.Controls.ItemsControl.OnItemCollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) + 0x52 bytes  
System.Windows.dll!System.Windows.Controls.ItemCollection.NotifyCollectionChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e) + 0x37 bytes   
System.Windows.dll!System.Windows.Controls.ItemCollection.NotifyItemsCollectionChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e) + 0x1f bytes  
System.Windows.dll!System.Windows.Controls.ItemCollection.EnumerableCollectionView.System.Windows.Controls.ICollectionChangedListener.OnCollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) + 0x4f bytes    
System.Windows.dll!System.Windows.Controls.WeakCollectionChangedListener.SourceCollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) + 0x3d bytes 
Microsoft.Practices.Composite.Presentation!Microsoft.Practices.Composite.Presentation.Regions.ViewsCollection.OnCollectionChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e = {System.Collections.Specialized.NotifyCollectionChangedEventArgs}) Line 102 + 0x24 bytes  C#
Microsoft.Practices.Composite.Presentation!Microsoft.Practices.Composite.Presentation.Regions.ViewsCollection.RemoveAndNotify(System.Collections.IList items = Count = 1) Line 45 + 0x2b bytes  C#
Microsoft.Practices.Composite.Presentation!Microsoft.Practices.Composite.Presentation.Regions.ViewsCollection.UnderlyingCollection_CollectionChanged(object sender = Count = 0, System.Collections.Specialized.NotifyCollectionChangedEventArgs e = {System.Collections.Specialized.NotifyCollectionChangedEventArgs}) Line 153 + 0xb bytes C#
System.Windows.dll!System.Collections.ObjectModel.ObservableCollection<Microsoft.Practices.Composite.Presentation.Regions.ItemMetadata>.OnCollectionChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e) + 0x37 bytes 
System.Windows.dll!System.Collections.ObjectModel.ObservableCollection<System.__Canon>.RemoveItem(int index) + 0xa1 bytes   
mscorlib.dll!System.Collections.ObjectModel.Collection<Microsoft.Practices.Composite.Presentation.Regions.ItemMetadata>.Remove(Microsoft.Practices.Composite.Presentation.Regions.ItemMetadata item) + 0x75 bytes   
Microsoft.Practices.Composite.Presentation!Microsoft.Practices.Composite.Presentation.Regions.Region.Remove(object view = {Kite.MyApp.SlUI.NavigationRegion.NavigationRegionView}) Line 230 + 0x1b bytes    C#

Answer 1

Check first that _regionManager.Regions["NavigationRegion"] actually exists and is non null like so

if (_regionManager.Regions["NavigationRegion"] != null)
{
        List<object> views = new List<object>(_regionManager.Regions["NavigationRegion"].Views);

        foreach (object view in views)
        {
            _regionManager.Regions["NavigationRegion"].Remove(view);
        }
}

It may be that NavigationRegion isnt set up properly, or there is a typo or something like that

Answer 2

use a for loop not foreach when modifying a collection