xaml:
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<TextBlock Height="30" Margin="125,132,0,0"
Name="textBlock1" Text="TextBlock"
Width="83" MouseMove="textBlock1_MouseMove" />
</Grid>
и код:
private void textBlock1_MouseMove(object sender, MouseEventArgs e)
{
TextBlock realSender = (TextBlock)sender;
var theParent = (Grid)realSender.Parent;
var position = e.GetPosition(theParent);
realSender.Margin = new Thickness(
position.X - realSender.Width / 2,
position.Y - realSender.Height / 2, 0, 0);
}