在datatemplate中绑定UserControl

Question

<DataTemplate DataType="{x:Type models:ViewModel}">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <DockPanel HorizontalAlignment="Stretch" common:CustomAttachedProperties.IsAccessKeyScope="True">
            <userControl:MyBanner DockPanel.Dock="Left" x:Name="UserBanner" EmergencyProtocolVisible="False" />
            <userControl:PageSummary DockPanel.Dock="Top" x:Name="_adminSummaryWithFooter"/>
            <userControl:Footer HorizontalAlignment="Stretch" VerticalAlignment="Bottom" x:Name="_myFooter" DataContext="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type userControl:PageSummary}}, Path=.}">
                <userControl:Footer.InnerContent>
                    <StackPanel Background="Red" Height="300px" Width="500px">

                    </StackPanel>
                </userControl:Footer.InnerContent>
            </userControl:Footer>
        </DockPanel>
    </Grid>
</DataTemplate>

我需要在Footer元素中使用Viewmodel Icommand。如果我尝试这个DataContext="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type userControl:PageSummary}}, Path=.}，无法找到元素。此外，我尝试使用ElementName，其他控件中指定了名称。

使用Scoop的图片，需要将AdminSummary对象引用到Footer中：

请咨询