WPF - MVVM - 如何将ComboBox的Selectchange事件binding到ViewModel

<ComboBox VerticalAlignment="Center" HorizontalAlignment="Left" MinWidth="120" Margin="10,0,0,0"
                              x:Name="cboTest" 
                              DisplayMemberPath="FamilyName"  
                              SelectedValuePath="IdFamily" 
                              IsReadOnly="True"
                              ItemsSource="{Binding ListFamily}"
                              SelectedValue="{Binding Path=ViewModel.SelectedFamilyNameID, Mode=TwoWay, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type UserControl}}}"
                              Validation.ErrorTemplate="{x:Null}"
                              Visibility="{Binding ComboBoxVisibility}"
                              >
                            <i:Interaction.Triggers>
                                <i:EventTrigger EventName="SelectionChanged">
                                    <i:InvokeCommandAction Command="{Binding FamilySelectionChangedCommand}"   
                                                       CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}},Path=DataContext}"/>
                                </i:EventTrigger>
                            </i:Interaction.Triggers>
                        </ComboBox>