模板

ItemContainerStyle可用来指定每个item的触发器

<ItemsControl Margin="10"
              ItemsSource="{Binding Source={StaticResource myTodoList}}">
  
  <ItemsControl.Template>
    <ControlTemplate TargetType="ItemsControl">
      <Border BorderBrush="Aqua" BorderThickness="1" CornerRadius="15">
        <ItemsPresenter/>
      Border>
    ControlTemplate>
  ItemsControl.Template>
  
  <ItemsControl.ItemsPanel>
    <ItemsPanelTemplate>
      <WrapPanel />
    ItemsPanelTemplate>
  ItemsControl.ItemsPanel>
  
  <ItemsControl.ItemTemplate>
    <DataTemplate>
      <DataTemplate.Resources>
        <Style TargetType="TextBlock">
          <Setter Property="FontSize" Value="18"/>
          <Setter Property="HorizontalAlignment" Value="Center"/>
        Style>
      DataTemplate.Resources>
      <Grid>
        <Ellipse Fill="Silver"/>
        <StackPanel>
          <TextBlock Margin="3,3,3,0"
                     Text="{Binding Path=Priority}"/>
          <TextBlock Margin="3,0,3,7"
                     Text="{Binding Path=TaskName}"/>
        StackPanel>
      Grid>
    DataTemplate>
  ItemsControl.ItemTemplate>
  
  <ItemsControl.ItemContainerStyle>
    <Style>
      <Setter Property="Control.Width" Value="100"/>
      <Setter Property="Control.Margin" Value="5"/>
      <Style.Triggers>
        <Trigger Property="Control.IsMouseOver" Value="True">
          <Setter Property="Control.ToolTip"
                  Value="{Binding RelativeSource={x:Static RelativeSource.Self},
                          Path=Content.Description}"/>
        Trigger>
      Style.Triggers>
    Style>
  ItemsControl.ItemContainerStyle>
ItemsControl>

下面是该示例在呈现时的屏幕快照：