Attribute is not allowed in property element

[Tearies]

<interactivity:Interaction.Behaviors xmlns:interactivity="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity">
<core:DataStateBehavior xmlns:core="clr-namespace:Microsoft.Expression.Interactivity.Core;assembly=Microsoft.Expression.Interactions" core:DataStateBehavior.TrueState="True" core:DataStateBehavior.FalseState="False" core:DataStateBehavior.Value="True" core:DataStateBehavior.Binding="{Binding VisualState}" />
</interactivity:Interaction.Behaviors>

it seems not compiled. error:Attribute is not allowed in property element