Wpf Dock Panel Dock left and Dock right

Question

I am not able to move buttons inside of a dock panel to the right, I tried few solutions, and after all I put them in stack panels and tried to move them to the right, but acctualy they wont move anywhere, here is how it looks:

And here is my code:

   <GroupStyle>
            <GroupStyle.ContainerStyle>
                <Style TargetType="{x:Type GroupItem}">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type GroupItem}">
                                <Expander IsExpanded="True"  Background="Black" Opacity="0.7">
                                    <Expander.Header>
                                        <DockPanel Height="50">
                                          <StackPanel Orientation="Horizontal" VerticalAlignment="Center" DockPanel.Dock="Right"> <Button DockPanel.Dock="Right" Content="Test" Margin="0,0,28,0"/></StackPanel>    
                                          <StackPanel Orientation="Horizontal" VerticalAlignment="Center" DockPanel.Dock="Left">  <TextBlock FontWeight="Normal" FontFamily="Verdana" FontSize="20" Height="25" Foreground="#83D744" Text="{Binding Path=Name,StringFormat= Order Number:# {0}}" /></StackPanel>
                                        </DockPanel>
                                    </Expander.Header>
                                    <Expander.Content>
                                        <ItemsPresenter />
                                    </Expander.Content>
                                </Expander>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </GroupStyle.ContainerStyle>
        </GroupStyle>
    </DataGrid.GroupStyle>

edit:

This above causes width on dock panel

<DockPanel Height="50" Width="{Binding ActualWidth, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=DataGrid}}">
                                        <Button DockPanel.Dock="Right" Content="Test" Margin="0,0,28,0"/>
                                        <TextBlock FontWeight="Normal" FontFamily="Verdana" FontSize="20" Height="25" Foreground="#83D744" Text="{Binding Path=Name,StringFormat= Order Number:# {0}}" />
                                    </DockPanel>

Answer 1

Try the following method. this works in my project

<DockPanel Height="50">
   <grid DockPanel.Dock="Right">
       <Button  Content="Test" Margin="0,0,28,0"/>
   </grid >    
   <grid DockPanel.Dock="Left">
       <TextBlock FontWeight="Normal" FontFamily="Verdana" FontSize="20" Height="25" Foreground="#83D744" Text="{Binding Path=Name,StringFormat= Order Number:# {0}}"/>
   </grid>
</DockPanel>            

Answer 2

Apply Width="{Binding ActualWidth, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=DataGrid}}" to your DockPanel and see if this solves your problem.