WPF TextBox 失去焦点绑定事件

[RelayCommand]
  private void LostFocus()
  {
      GrowlTool.ShowError("123");
  }

<TextBox
    MinWidth="100"
    hc:BorderElement.CornerRadius="0"
    IsReadOnly="{Binding ElementName=CalModeComboBox, Path=SelectedIndex, Converter={StaticResource CalModeToBoolConverter}}"
    Style="{StaticResource TextBoxBaseBaseStyle}"
    Text="{Binding Curve.CrtFactor[0], StringFormat=0.###}"
    TextAlignment="Center">
    <hc:Interaction.Triggers>
        <hc:EventTrigger EventName="LostFocus">
            <hc:InvokeCommandAction Command="{Binding LostFocusCommand}" />
        </hc:EventTrigger>
    </hc:Interaction.Triggers>
</TextBox>