Horizontal StackPanel
will ignore HorizontalAlignment
of its children but you can use Grid
instead with 3 StackPanel
aligned left, centre and right:
<Grid Grid.Row="2" Grid.ColumnSpan="2">
<StackPanel Orientation="Horizontal" HorizontalAlignment="Left">
<TextBlock Margin="10">Filter By Date</TextBlock>
<CheckBox Margin="2" Height="18" Width="13"></CheckBox>
</StackPanel>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
<TextBlock Margin="10">Begin Date</TextBlock>
<DatePicker Margin="2"> </DatePicker>
</StackPanel>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
<TextBlock Margin="10">End Date</TextBlock>
<DatePicker Margin="2"></DatePicker>
</StackPanel>
</Grid>