WPF控件TextBlock文本居中

<TextBlock 
            Grid.Row="7" HorizontalAlignment="Center" VerticalAlignment="Center"
            Style="{StaticResource LoginTitle}" 
            FontSize="21" Foreground="#3C6368" 
            Block.TextAlignment="Center"
            TextWrapping="WrapWithOverflow">
            aaaaa<LineBreak/>
            bbbbb<LineBreak/>
        </TextBlock>

设置Block.TextAlignment="Center"即可