这是关于基本 XAML 概念的一个非常重要的问题：ItemsControl 数据绑定。 C# 中的所有 ItemsControls 都能够获取数据类（称为“Items”）并将它们转换为可视 UIElements（称为“Containers”）。例如，ListBox 可以从其 ItemSource 中获取项目，创建新的 ListBoxItems 并将每个项目设置为其容器的 DataContext。这基本上就是所有 ItemsControl 的数据绑定工作方式。
为什么这很有趣？因为 LongListMultiSelector 是另一个 ItemsControl，它会生成 LongListMultiSelectorItems。在 ListBoxItem 和 LongListMultiSelectorItem 的情况下，实例化的 DataTemplate 都嵌套在 ItemTemplate 内，它只是容器的一部分。但是，您无法从 DataTemplate 内部控制容器的属性。这就是为什么您在这里所做的一切似乎都不起作用的原因。
解决方案：使用 ItemContainerStyle 更改容器本身的属性。
1) 在具有以下 C# 和 XAML 代码的项目中打开 blend：
this.DataContext = "foo bar baz".Split(' ');
<Toolkit:LongListMultiSelector ItemsSource="{Binding}">
<Toolkit:LongListMultiSelector.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}" />
</DataTemplate>
</Toolkit:LongListMultiSelector.ItemTemplate>
</Toolkit:LongListMultiSelector>
2) 选择 LongListMultiSelector。在顶部菜单上选择“对象--> 编辑附加样式--> 编辑ItemContainerSyle--> 创建空”并点击“确定”。
3) 由于 LongListMultiSelectorItem 在 Grid 和 List 之间更改了 ItemContainerStyle，因此您需要手动将您的样式中的所有 <Setter /> 元素替换为以下任一样式中的所有 setter。例如，我将 LongListMultiSelectorItemListStyle 中的所有设置器复制到我的新 LongListMultiSelectorItemStyle1 中。
<Style x:Key="LongListMultiSelectorItemGridStyle" TargetType="controls:LongListMultiSelectorItem">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="BorderThickness" Value="0"/>
<Setter Property="BorderBrush" Value="Transparent"/>
<Setter Property="Padding" Value="0"/>
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
<Setter Property="VerticalContentAlignment" Value="Stretch"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="controls:LongListMultiSelectorItem">
<Border x:Name="LayoutRoot" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" HorizontalAlignment="{TemplateBinding HorizontalAlignment}" VerticalAlignment="{TemplateBinding VerticalAlignment}">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver"/>
<VisualState x:Name="Disabled">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="LayoutRoot">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource TransparentBrush}"/>
</ObjectAnimationUsingKeyFrames>
<DoubleAnimation Duration="0" To=".5" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="ContentContainer"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="SelectionStates">
<VisualState x:Name="Unselected"/>
<VisualState x:Name="Selected">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="SelectionTriangle">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="SelectionCheck">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="HasSelectionStates">
<VisualState x:Name="Opened">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="SelectionRectangle">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="OuterCover">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Closed"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Grid Margin="1" >
<ContentControl x:Name="ContentContainer"
Margin="3"
ContentTemplate="{TemplateBinding ContentTemplate}"
Content="{TemplateBinding Content}"
Foreground="{TemplateBinding Foreground}"
HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
/>
<Rectangle x:Name="SelectionRectangle" Visibility="Collapsed"
Stroke="{StaticResource PhoneAccentBrush}" StrokeThickness="2"/>
<Polyline x:Name="SelectionTriangle" Visibility="Collapsed"
HorizontalAlignment="Right" VerticalAlignment="Top"
Points="50,0 50,50 0,0"
Fill="{StaticResource PhoneAccentBrush}"
/>
<Polyline x:Name="SelectionCheck" Visibility="Collapsed"
Margin="5" HorizontalAlignment="Right" VerticalAlignment="Top"
Points="40,0 43,3 28,18 18,8 21,5 28,12"
Fill="{StaticResource PhoneForegroundBrush}"
/>
<Grid x:Name="OuterCover" IsHitTestVisible="True" Visibility="Collapsed" Background="Transparent" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"/>
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="LongListMultiSelectorItemListStyle" TargetType="controls:LongListMultiSelectorItem">
<Style.Setters>
<Setter Property="Background" Value="{StaticResource PhoneAccentBrush}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="controls:LongListMultiSelectorItem">
<Grid MinHeight="52">
<Grid.Resources>
<ExponentialEase EasingMode="EaseIn" Exponent="8" x:Key="ExponentialEaseIn"/>
<QuadraticEase EasingMode="EaseOut" x:Key="QuadraticEaseOut"/>
</Grid.Resources>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="SelectionEnabledStates">
<VisualStateGroup.Transitions>
<VisualTransition x:Name="ClosedToExposed"
From="Closed" To="Exposed"
GeneratedDuration="0:0:0.30">
<Storyboard>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Opacity)"
Storyboard.TargetName="OuterHintPanel">
<EasingDoubleKeyFrame KeyTime="0:0:0.0" Value="0.0" EasingFunction="{StaticResource QuadraticEaseOut}"/>
<EasingDoubleKeyFrame KeyTime="0:0:0.30" Value="1.0" EasingFunction="{StaticResource QuadraticEaseOut}"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</VisualTransition>
<VisualTransition x:Name="ExposedToClosed"
From="Exposed" To="Closed"
GeneratedDuration="0:0:0.30">
<Storyboard>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Opacity)"
Storyboard.TargetName="OuterHintPanel">
<EasingDoubleKeyFrame KeyTime="0:0:0.0" Value="1.0" EasingFunction="{StaticResource QuadraticEaseOut}"/>
<EasingDoubleKeyFrame KeyTime="0:0:0.30" Value="0.0" EasingFunction="{StaticResource QuadraticEaseOut}"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</VisualTransition>
<VisualTransition x:Name="ExposedToOpened"
From="Exposed" To="Opened"
GeneratedDuration="0:0:0.30">
<Storyboard>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)"
Storyboard.TargetName="SelectBox">
<EasingDoubleKeyFrame KeyTime="0:0:0.0" Value="-58" EasingFunction="{StaticResource ExponentialEaseIn}"/>
<EasingDoubleKeyFrame KeyTime="0:0:0.15" Value="0" EasingFunction="{StaticResource ExponentialEaseIn}"/>
</DoubleAnimationUsingKeyFrames>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)"
Storyboard.TargetName="Presenter">
<EasingDoubleKeyFrame KeyTime="0:0:0.0" Value="24" EasingFunction="{StaticResource ExponentialEaseIn}"/>
<EasingDoubleKeyFrame KeyTime="0:0:0.15" Value="86" EasingFunction="{StaticResource ExponentialEaseIn}"/>
</DoubleAnimationUsingKeyFrames>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Opacity)"
Storyboard.TargetName="OuterHintPanel">
<EasingDoubleKeyFrame KeyTime="0:0:0.0" Value="1.0" EasingFunction="{StaticResource QuadraticEaseOut}"/>
<EasingDoubleKeyFrame KeyTime="0:0:0.30" Value="0.0" EasingFunction="{StaticResource QuadraticEaseOut}"/>
</DoubleAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)"
Storyboard.TargetName="SelectBox">
<DiscreteObjectKeyFrame KeyTime="0:0:0.0" Value="Visible"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.IsHitTestVisible)"
Storyboard.TargetName="OuterHintPanel">
<DiscreteObjectKeyFrame KeyTime="0:0:0" Value="False"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.IsHitTestVisible)"
Storyboard.TargetName="InnerHintPanel">
<DiscreteObjectKeyFrame KeyTime="0:0:0" Value="False"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualTransition>
<VisualTransition x:Name="ClosedToOpened"
From="Closed" To="Opened"
GeneratedDuration="0:0:0.15">
<Storyboard>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)"
Storyboard.TargetName="SelectBox">
<EasingDoubleKeyFrame KeyTime="0:0:0.0" Value="-58" EasingFunction="{StaticResource ExponentialEaseIn}"/>
<EasingDoubleKeyFrame KeyTime="0:0:0.15" Value="0" EasingFunction="{StaticResource ExponentialEaseIn}"/>
</DoubleAnimationUsingKeyFrames>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)"
Storyboard.TargetName="Presenter">
<EasingDoubleKeyFrame KeyTime="0:0:0.0" Value="24" EasingFunction="{StaticResource ExponentialEaseIn}"/>
<EasingDoubleKeyFrame KeyTime="0:0:0.15" Value="86" EasingFunction="{StaticResource ExponentialEaseIn}"/>
</DoubleAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)"
Storyboard.TargetName="SelectBox">
<DiscreteObjectKeyFrame KeyTime="0:0:0.0" Value="Visible"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.IsHitTestVisible)"
Storyboard.TargetName="OuterHintPanel">
<DiscreteObjectKeyFrame KeyTime="0:0:0" Value="False"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.IsHitTestVisible)"
Storyboard.TargetName="InnerHintPanel">
<DiscreteObjectKeyFrame KeyTime="0:0:0" Value="False"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualTransition>
<VisualTransition x:Name="OpenedToClosed"
From="Opened" To="Closed"
GeneratedDuration="0:0:0.15">
<Storyboard>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)"
Storyboard.TargetName="SelectBox">
<EasingDoubleKeyFrame KeyTime="0:0:0.0" Value="0" EasingFunction="{StaticResource ExponentialEaseIn}"/>
<EasingDoubleKeyFrame KeyTime="0:0:0.15" Value="-58" EasingFunction="{StaticResource ExponentialEaseIn}"/>
</DoubleAnimationUsingKeyFrames>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)"
Storyboard.TargetName="Presenter">
<EasingDoubleKeyFrame KeyTime="0:0:0.0" Value="86" EasingFunction="{StaticResource ExponentialEaseIn}"/>
<EasingDoubleKeyFrame KeyTime="0:0:0.15" Value="24" EasingFunction="{StaticResource ExponentialEaseIn}"/>
</DoubleAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)"
Storyboard.TargetName="SelectBox">
<DiscreteObjectKeyFrame KeyTime="0:0:0.15" Value="Collapsed"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualTransition>
</VisualStateGroup.Transitions>
<VisualStateGroup.States>
<VisualState x:Name="Closed"/>
<VisualState x:Name="Exposed">
<Storyboard>
<DoubleAnimation Storyboard.TargetProperty="(UIElement.Opacity)"
Storyboard.TargetName="OuterHintPanel"
Duration="0" To="1.0"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Opened">
<Storyboard>
<DoubleAnimation Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)"
Storyboard.TargetName="SelectBox"
Duration="0" To="0"/>
<DoubleAnimation Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateX)"
Storyboard.TargetName="Presenter"
Duration="0" To="86"/>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)"
Storyboard.TargetName="SelectBox">
<DiscreteObjectKeyFrame KeyTime="0:0:0" Value="Visible"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)"
Storyboard.TargetName="OuterCover">
<DiscreteObjectKeyFrame KeyTime="0:0:0" Value="Visible"/>
</ObjectAnimationUsingKeyFrames>
<DoubleAnimation Storyboard.TargetProperty="(UIElement.Opacity)"
Storyboard.TargetName="OuterHintPanel"
Duration="0" To="0.0"/>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.IsHitTestVisible)"
Storyboard.TargetName="OuterHintPanel">
<DiscreteObjectKeyFrame KeyTime="0:0:0" Value="False"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.IsHitTestVisible)"
Storyboard.TargetName="InnerHintPanel">
<DiscreteObjectKeyFrame KeyTime="0:0:0" Value="False"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup.States>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Grid HorizontalAlignment="Stretch">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid Grid.Column="0" HorizontalAlignment="Stretch" primitives:ClipToBounds.IsEnabled="True">
<ContentPresenter x:Name="Presenter">
<ContentPresenter.RenderTransform>
<CompositeTransform TranslateX="24"/>
</ContentPresenter.RenderTransform>
</ContentPresenter>
</Grid>
<Rectangle x:Name="InnerHintPanel" Grid.Column="0" Width="24"
Height="{TemplateBinding HintPanelHeight}"
HorizontalAlignment="Left"
Fill="Transparent"
StrokeThickness="0">
<Rectangle.RenderTransform>
<CompositeTransform TranslateX="24"/>
</Rectangle.RenderTransform>
</Rectangle>
<ContentControl x:Name="InfoPresenter" Grid.Column="1"
VerticalAlignment="Top"
Content="{TemplateBinding ContentInfo}"
ContentTemplate="{TemplateBinding ContentInfoTemplate}"/>
</Grid>
<Rectangle x:Name="OuterHintPanel" Width="24"
HorizontalAlignment="Left"
Height="{TemplateBinding HintPanelHeight}"
Fill="{TemplateBinding Background}"
StrokeThickness="0" Opacity="0.0"/>
<Grid x:Name="OuterCover" IsHitTestVisible="True"
Visibility="Collapsed" Background="Transparent"/>
<Canvas HorizontalAlignment="Left">
<CheckBox x:Name="SelectBox" VerticalAlignment="Top" Margin="12,-20,5,0" Visibility="Collapsed"
IsChecked="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=IsSelected, Mode=TwoWay}">
<CheckBox.RenderTransform>
<CompositeTransform TranslateX="-58"/>
</CheckBox.RenderTransform>
</CheckBox>
</Canvas>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style.Setters>
</Style>
4) 确保修复 XMLNS 引用，例如 toolkit 和 primitives。
5) 现在您可以编辑样式了。从顶部菜单转到“对象--> 编辑附加样式--> 编辑ItemContainerStyle--> 编辑当前”。
6) 将 ItemContainerStyle Margin 从“0”设置为“0, 0, 50, 0”。
当我们使用修改后的 ItemContainerStyle 运行 LongListMultiSelector 时，我们可以看到项目之间的以下空格：
重要的是要记住，ItemContainerStyle 是我们武器库中非常强大的武器。我们可以使用 ItemContainerStyle 来编辑容器的样式，甚至是它们的模板。