In the .net7 CollectionViewSource has a different behaviour than in the .net6

Basically, in .net7 when you run the attached project and press the button, it will display a list of items. If you run the unit test it will throw an exception on this line

EntityCollectionView = new CollectionViewSource { Source = Entities }.View;

Because the View is null.

If you change the TargetFramework to net6 the test passes because View contains an instance.

Is this a bug?

Regards Daniel Kaczmarek

WpfApp2.zip

[steveharter]

Appears to be related or a duplicate of https://github.com/dotnet/wpf/issues/7205

Callstack:

   System.NullReferenceException : Object reference not set to an instance of an object.
  Stack Trace:
   at System.Windows.StyleHelper.GetExpression(DependencyObject d, DependencyProperty dp)
   at System.Windows.Data.BindingOperations.GetBindingExpressionBase(DependencyObject target, DependencyProperty dp)
   at System.Windows.Data.CollectionViewSource.<EnsureView>b__103_0(Object x)
   at MS.Internal.Data.ViewManager.EnsureCollectionRecord(Object collection, Func`2 GetSourceItem)
   at MS.Internal.Data.ViewManager.GetExistingView(Object collection, CollectionViewSource cvs, Type collectionViewType, Func`2 GetSourceItem)
   at MS.Internal.Data.ViewManager.GetViewRecord(Object collection, CollectionViewSource cvs, Type collectionViewType, Boolean createView, Func`2 GetSourceItem)
   at MS.Internal.Data.DataBindEngine.GetViewRecord(Object collection, CollectionViewSource key, Type collectionViewType, Boolean createView, Func`2 GetSourceItem)
   at System.Windows.Data.CollectionViewSource.EnsureView(Object source, Type collectionViewType)
   at System.Windows.DependencyObject.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 WpfApp2.MainWindowViewModel.CreateEntityCollectionView() in C:\temp\Wpf2App\WpfApp2\WpfApp2\MainWindowViewModel.cs:line 33
   at TestProject1.Tests.Test1() in C:\temp\Wpf2App\WpfApp2\TestProject1\UnitTest1.cs:line 18
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr)

[ThomasGoulet73]

I believe the fix is already in the release/7.0 branch but it was not included in a public release yet. It should be included in the upcoming .Net 7.0.3.