WPF databinding to a property in the same control

In this example the IsEnabled property of my button is bound to the selected rows "Local" property of the grid and it works just fine:

        <Button DockPanel.Dock="Bottom" Width="100" Height="100" IsEnabled="{Binding ElementName=dataGridRestore , Path=SelectedItem.Local}"></Button>

        <my:DataGrid x:Name="dataGridRestore" 
                     ItemsSource="{Binding}" 
                     >

            <my:DataGrid.ContextMenu>
                <ContextMenu Name="restoreCntextMenu">
                    <MenuItem Header="Open" />
                </ContextMenu>
            </my:DataGrid.ContextMenu>

            <my:DataGridCheckBoxColumn Header="Local" Binding="{Binding Local}"  />
        </my:DataGrid>

Now when I move the button from outside my grid to inside the context menu of the grid my binding doesn't work. Why is this and how can i fix it?

        <my:DataGrid x:Name="dataGridRestore" 
                     ItemsSource="{Binding}" 
                     >

            <my:DataGrid.ContextMenu>
                <ContextMenu Name="restoreCntextMenu">
                    <MenuItem Header="Open"开发者_如何学Python />
                    <Button  Width="100" Height="100" IsEnabled="{Binding ElementName=dataGridRestore , Path=SelectedItem.Local}"></Button>
                </ContextMenu>
            </my:DataGrid.ContextMenu>

            <my:DataGridCheckBoxColumn Header="Local" Binding="{Binding Local}"  />
        </my:DataGrid>

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Use this code:

<ContextMenu DataContext="{Binding PlacementTarget.SelectedItem, RelativeSource={RelativeSource Self}}">
    <Button IsEnabled="{Binding Local}"/>
</ContextMenu>

I tested it with ContextMenu of DataGridRows and it worked fine.

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What about using the RelativeSource attribute instead of the ElementName?

can't test it right now but something like this :

<Button  Width="100" Height="100" IsEnabled="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type my:DataGrid}},Path=SelectedItem.Local}"></Button>