关键在于你写的事件触发命令在应用模板的控件的datacontext中，而不在DataTemplate中
<i:Interaction.Triggers> <i:EventTrigger EventName="SelectedItemChanged"> <prism:InvokeCommandAction Command="{Binding SelectedItemChangedCommand}" TriggerParameterPath="Source"/> </i:EventTrigger> </i:Interaction.Triggers>