Horizo​​ntalAlignment在DataGridTextColumn中的ComboBox上不起作用

Question

I have a DataGridTextColumn whose header consists of a TextBlock and a ComboBox . I would like the TextBlock to be left aligned and the ComboBox to be right-aligned. When I try setting that on ComboBox using HorizontalAlignment = "Right" , it does not work! For the header I tried with StackPanel as well as a Grid for containing the TextBlock and ComboBox . What I am doing wrong?

    <DataGrid 
        CanUserSortColumns="True"
        IsReadOnly="True">

        <DataGrid.Columns>
            <DataGridTextColumn Header="Time"/>

            <DataGridTextColumn>

                <DataGridTextColumn.Header>

                    <StackPanel Orientation="Horizontal">
                        <TextBlock Text="Money" VerticalAlignment="Center"/>
                        <ComboBox HorizontalAlignment="Right" VerticalAlignment="Center"
                            Width="100" ItemsSource="{Binding comboBoxItems}" SelectedIndex="0">
                        </ComboBox>
                    </StackPanel>
                </DataGridTextColumn.Header>

            </DataGridTextColumn>

        </DataGrid.Columns>
    </DataGrid>

Attempt with Grid:

                <DataGridTextColumn.Header>

                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto"/>
                            <ColumnDefinition Width="*"/>
                        </Grid.ColumnDefinitions>
                        <TextBlock Grid.Column="0" Text="Money" VerticalAlignment="Center"/>
                        <ComboBox Grid.Column="1" HorizontalAlignment="Right" VerticalAlignment="Center"
                            ItemsSource="{Binding comboBoxItems}" SelectedIndex="0">
                        </ComboBox>
                    </Grid>

                </DataGridTextColumn.Header>

EDIT 1: I would like the ComboBox to be stretched if the column is dragged to increase the column width. Otherwise atleast the ComboBox should align to the right if the column is dragged on the right side.

EDIT 2: The important thing here is that when I drag the column to increase its width, the ComboBox should fall on the right side.

Answer 1

use this

<DataGridTextColumn Width="120">
    <DataGridTextColumn.HeaderTemplate>
        <DataTemplate>
            <Grid Width="{Binding Path=ActualWidth, RelativeSource={RelativeSource AncestorType={x:Type DataGridColumnHeader}}}">
                <TextBlock Text="LLLLL" HorizontalAlignment="Left" Margin="5"/>
                <TextBlock Text="RRRRR" HorizontalAlignment="Right" Margin="5"/>
            </Grid>
        </DataTemplate>
    </DataGridTextColumn.HeaderTemplate>
</DataGridTextColumn>

Answer 2

Try DockPanel instead of StackPanel .

<DockPanel LastChildFill="True">
        <TextBlock Text="Money" VerticalAlignment="Center" DockPanel.Dock="Left"/>
        <ComboBox  VerticalAlignment="Center" SelectedIndex="0"/>
</DockPanel>