TextBox Alignment When Printing From UWP - xaml

Question

I'm trying to print a page of text from a UWP app, but I'm having a problem with alignment. First of all, I've created a Page which contains the following xaml:
<Grid Background="White">
<TextBlock Text="Welcome Printed World!" FontSize="36" Foreground="Black" HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Grid>
Notice how the TextBlock is aligned to be centered within the grid.
Then, I print it using the various PrintDocument event handlers; this the code to print preview it (simplified to ignore margins and the non-printable area):
Page printPage;
private void OnPrintDocumentPaginate(object sender, PaginateEventArgs e)
{
// Construct an instance of the page to print, and tell Windows that there is only 1 page
this.printPage = new PrintPage();
printDocument.SetPreviewPageCount(1, PreviewPageCountType.Final);
}
private void OnPrintDocumentGetPreviewPage(object sender, GetPreviewPageEventArgs e)
{
// Give Windows a reference to the page to print for preview
this.printDocument.SetPreviewPage(e.PageNumber, this.printPage);
}
And this is how it prints:
Notice that the TextBlock is not centered.
However, if I wrap the TextBlock in a border, like this:
<Grid Background="White">
<Border HorizontalAlignment="Center" VerticalAlignment="Center">
<TextBlock Text="Welcome Printed World!" FontSize="36" Foreground="Black"/>
</Border>
</Grid>
Then it is fine:
Can anybody see why the TextBlock is not centred when using the original xaml?

Answer 1

I experienced the same problem when upgrading from Windows 8.1 to UWP project.
When printing in UWP, the TextBlock.VerticalAlignment and TextBlock.HorizontalAlignment properties do not work as expected.
However, if you use a Run element instead of the TextBlock.Text property, they appear to work as expected:
<TextBlock FontSize="36" Foreground="Black" HorizontalAlignment="Center" VerticalAlignment="Center">
<Run Text="Welcome Printed World!" />
</TextBlock>
Alternatively you can use TextBlock.Margin for vertical alignment and TextBlock.TextAlignment for horizontal alignment.