update ListBox when updating or deltying

Question

hi There, im creating an composite application with wpf and CAl,my problem si that my listbox doesn't update it's data when i updated thme even if it's so in the database,here is the code:

    <CollectionViewSource x:Key="cvs" Source="{Binding Path=Etudiants,Mode=OneWay}">
        <CollectionViewSource.SortDescriptions>
            <scm:SortDescription PropertyName="FullName" Direction="Ascending" />
        </CollectionViewSource.SortDescriptions>
    </CollectionViewSource>

thanks's for the help