如果展开 DataGrid ControlTemplate,您会看到有一个绑定到 SelectAllCommand 的 Button。
<Window x:Class="WpfApplication1.Window3"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:toolkit="http://schemas.microsoft.com/wpf/2008/toolkit"
Title="Window3" Height="500" Width="500"
Loaded="Window_Loaded">
<Window.Resources>
<Style x:Key="DataGridStyle1" TargetType="{x:Type toolkit:DataGrid}">
<Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="BorderBrush" Value="#FF688CAF"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="RowDetailsVisibilityMode" Value="VisibleWhenSelected"/>
<Setter Property="ScrollViewer.CanContentScroll" Value="True"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type toolkit:DataGrid}">
<Border SnapsToDevicePixels="True" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
<ScrollViewer x:Name="DG_ScrollViewer" Focusable="False">
<ScrollViewer.Template>
<ControlTemplate TargetType="{x:Type ScrollViewer}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Button Command="{x:Static toolkit:DataGrid.SelectAllCommand}"
Width="{Binding CellsPanelHorizontalOffset, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type toolkit:DataGrid}}}" Focusable="False">
<Button.Template>
<ControlTemplate TargetType="{x:Type Button}">
<Grid>
<Rectangle x:Name="Border" Fill="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" SnapsToDevicePixels="True"/>
<Polygon x:Name="Arrow" Fill="Black" Stretch="Uniform" HorizontalAlignment="Right" Margin="8,8,3,3" VerticalAlignment="Bottom" Opacity="0.15" Points="0,10 10,10 10,0"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Stroke" TargetName="Border" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/>
</Trigger>
<Trigger Property="IsPressed" Value="True">
<Setter Property="Fill" TargetName="Border" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/>
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Visibility" TargetName="Arrow" Value="Collapsed"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Button.Template>
<Button.Visibility>
<Binding Path="HeadersVisibility" RelativeSource="{RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type toolkit:DataGrid}}">
<Binding.ConverterParameter>
<toolkit:DataGridHeadersVisibility>All</toolkit:DataGridHeadersVisibility>
</Binding.ConverterParameter>
</Binding>
</Button.Visibility>
</Button>
<toolkit:DataGridColumnHeadersPresenter x:Name="PART_ColumnHeadersPresenter" Grid.Column="1">
<toolkit:DataGridColumnHeadersPresenter.Visibility>
<Binding Path="HeadersVisibility" RelativeSource="{RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type toolkit:DataGrid}}">
<Binding.ConverterParameter>
<toolkit:DataGridHeadersVisibility>Column</toolkit:DataGridHeadersVisibility>
</Binding.ConverterParameter>
</Binding>
</toolkit:DataGridColumnHeadersPresenter.Visibility>
</toolkit:DataGridColumnHeadersPresenter>
<ScrollContentPresenter x:Name="PART_ScrollContentPresenter" Content="{TemplateBinding Content}" ContentStringFormat="{TemplateBinding ContentStringFormat}" ContentTemplate="{TemplateBinding ContentTemplate}" Grid.ColumnSpan="2" Grid.Row="1" CanContentScroll="{TemplateBinding CanContentScroll}" CanHorizontallyScroll="False" CanVerticallyScroll="False"/>
<ScrollBar x:Name="PART_VerticalScrollBar" Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}" Grid.Column="2" Grid.Row="1" Maximum="{TemplateBinding ScrollableHeight}" Value="{Binding VerticalOffset, Mode=OneWay, RelativeSource={RelativeSource TemplatedParent}}" Orientation="Vertical" ViewportSize="{TemplateBinding ViewportHeight}"/>
<Grid Grid.Column="1" Grid.Row="2">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="{Binding NonFrozenColumnsViewportHorizontalOffset, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type toolkit:DataGrid}}}"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<ScrollBar x:Name="PART_HorizontalScrollBar" Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}" Grid.Column="1" Maximum="{TemplateBinding ScrollableWidth}" Value="{Binding HorizontalOffset, Mode=OneWay, RelativeSource={RelativeSource TemplatedParent}}" Orientation="Horizontal" ViewportSize="{TemplateBinding ViewportWidth}"/>
</Grid>
</Grid>
</ControlTemplate>
</ScrollViewer.Template>
<ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</ScrollViewer>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsGrouping" Value="True">
<Setter Property="ScrollViewer.CanContentScroll" Value="False"/>
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Grid>
<toolkit:DataGrid Name="dataGrid"
ItemsSource="{Binding}"
CanUserResizeRows="False"
SelectionMode="Extended"
AutoGenerateColumns="True" Style="{DynamicResource DataGridStyle1}">
<toolkit:DataGrid.RowHeaderTemplate>
<DataTemplate>
<Grid>
<CheckBox IsChecked="{
Binding Path=IsSelected,
Mode=TwoWay,
RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type toolkit:DataGridRow}}}"
/>
</Grid>
</DataTemplate>
</toolkit:DataGrid.RowHeaderTemplate>
</toolkit:DataGrid>
</Grid>
You can override that Button's Command to perform your own logic or even replace the button with a different control.