Custom DataGrid control with ControlTemplate and ContentPresenter

Question

I have a custom DataGrid (I extended it and included a DependencyProperty Label), I am using the DataGrid and wanted to add Label control using ControlTemplate and ContentPresenter. In the ContentTemplate the DependencyProperty Label works and displays as it should, but the ContentPresenter doesn't work or display any of the DataGrid control at all. I tried it with ItemsPresenter and it shows the rows, I was wondering if there is a way to display the DataGrid using ContentPresenter in this manner? what's the right approach to doing this?

MyUserControl.xaml

<UserControl
    x:Class="MyNamespace.UI.MyUserControl"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
     xmlns:e="clr-namespace:MyNamespace.UI"
     mc:Ignorable="d" 
     d:DesignHeight="350" d:DesignWidth="400">
    <UserControl.Resources>
        <Style TargetType="{x:Type e:DataGrid}"  BasedOn="{StaticResource {x:Type DataGrid}}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type e:DataGrid}">
                        <StackPanel>
                            <Label Content="{Binding Label, RelativeSource={RelativeSource TemplatedParent}}" ContentStringFormat="{}{0}: " />
                            <ContentPresenter Margin="2" HorizontalAlignment="Center" VerticalAlignment="Center"/>
                        </StackPanel>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </UserControl.Resources>
    <WrapPanel  x:Name="LayoutRoot" Width="900" HorizontalAlignment="Stretch" Margin="12" VerticalAlignment="Stretch">
        <e:DataGrid Label="My Label 1"     ItemsSource="{Binding Source={StaticResource MySource1}}"/>
        <e:DataGrid Label="My Label 2"     ItemsSource="{Binding Source={StaticResource MySource2}}"/>
    </WrapPanel>
</UserControl>

DataGrid.cs

namespace MyNamespace.UI
{
    public class DataGrid : System.Windows.Controls.DataGrid
    {
        public string Label
        {
            get { return (string)GetValue(LabelProperty); }
            set { SetValue(LabelProperty, value); }
        }

        public static readonly DependencyProperty LabelProperty =
            DependencyProperty.Register("Label", typeof(string), typeof(DataGrid), new UIPropertyMetadata(""));

        public DataGrid()
        {}
    }
}

Answer 1

The ControlTemplate defines the appearance of the entire control. So you can't simply put a <ContentPresenter /> in your template and expect a DataGrid to show up. Also, you cannot inherit only part of a ControlTemplate:

WPF: Is there a way to override part of a ControlTemplate without redefining the whole style?

You could copy the entire default template and add your Label to it though:

<Style TargetType="{x:Type e:DataGrid}"  BasedOn="{StaticResource {x:Type DataGrid}}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type DataGrid}">
                <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="True">
                    <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="Auto"/>
                                        <RowDefinition Height="*"/>
                                        <RowDefinition Height="Auto"/>
                                    </Grid.RowDefinitions>
                                    <Label Content="{Binding Label, RelativeSource={RelativeSource TemplatedParent}}" ContentStringFormat="{}{0}: " />
                                    <Button Grid.Row="1" Command="{x:Static DataGrid.SelectAllCommand}" Focusable="false" Style="{DynamicResource {ComponentResourceKey ResourceId=DataGridSelectAllButtonStyle, TypeInTargetAssembly={x:Type DataGrid}}}" Visibility="{Binding HeadersVisibility, ConverterParameter={x:Static DataGridHeadersVisibility.All}, Converter={x:Static DataGrid.HeadersVisibilityConverter}, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}" Width="{Binding CellsPanelHorizontalOffset, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
                                    <DataGridColumnHeadersPresenter x:Name="PART_ColumnHeadersPresenter" Grid.Row="1" Grid.Column="1" Visibility="{Binding HeadersVisibility, ConverterParameter={x:Static DataGridHeadersVisibility.Column}, Converter={x:Static DataGrid.HeadersVisibilityConverter}, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
                                    <ScrollContentPresenter x:Name="PART_ScrollContentPresenter" CanContentScroll="{TemplateBinding CanContentScroll}" Grid.ColumnSpan="2" Grid.Row="2"/>
                                    <ScrollBar x:Name="PART_VerticalScrollBar" Grid.Column="2" Maximum="{TemplateBinding ScrollableHeight}" Orientation="Vertical" Grid.Row="2" Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}" Value="{Binding VerticalOffset, Mode=OneWay, RelativeSource={RelativeSource TemplatedParent}}" ViewportSize="{TemplateBinding ViewportHeight}"/>
                                    <Grid Grid.Column="1" Grid.Row="3">
                                        <Grid.ColumnDefinitions>
                                            <ColumnDefinition Width="{Binding NonFrozenColumnsViewportHorizontalOffset, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
                                            <ColumnDefinition Width="*"/>
                                        </Grid.ColumnDefinitions>
                                        <ScrollBar x:Name="PART_HorizontalScrollBar" Grid.Column="1" Maximum="{TemplateBinding ScrollableWidth}" Orientation="Horizontal" Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}" Value="{Binding HorizontalOffset, Mode=OneWay, RelativeSource={RelativeSource TemplatedParent}}" ViewportSize="{TemplateBinding ViewportWidth}"/>
                                    </Grid>
                                </Grid>
                            </ControlTemplate>
                        </ScrollViewer.Template>
                        <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                    </ScrollViewer>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Style.Triggers>
        <MultiTrigger>
            <MultiTrigger.Conditions>
                <Condition Property="IsGrouping" Value="true"/>
                <Condition Property="VirtualizingPanel.IsVirtualizingWhenGrouping" Value="false"/>
            </MultiTrigger.Conditions>
            <Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
        </MultiTrigger>
    </Style.Triggers>
</Style>