TextBlock
doesn't support vertical alignment of its content. If you must use TextBlock
then you have to align it with respect to its parent.
However if you can use Label
instead (and they do have very similar functionality) then you can position the text content:
<Label VerticalContentAlignment="Center" HorizontalContentAlignment="Center">
I am centred text!
</Label>
The Label
will stretch to fill its bounds by default, meaning the label's text will be centred.