Collectionviewsource not updating the property in viewmodel

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C#

XAML

WPF

C#4.0

<cmc:AutoRefreshCollectionViewSource
             x:Uid="CollectionViewSource_1" x:Key='sortedList'
                              Source="{Binding Path=MyList, Mode=TwoWay}" >
                <cmc:AutoRefreshCollectionViewSource.SortDescriptions>
                    <scm:SortDescription x:Uid="scm:SortDescription_1" PropertyName="HoldingRegister"
                                     Direction="Ascending" />
                </cmc:AutoRefreshCollectionViewSource.SortDescriptions>
            </cmc:AutoRefreshCollectionViewSource>

This collectionViewSource is binded to a list view
As the above code MyList the Observable collection in ViewModel


here sorting is happening but the collectionviewsource is not updating back to MyList

pls advice to solve this problem