Hi Venkateshwaran,
Thanks for the demo - it works great! and I appreciate the detail which you added to show a bit the complexity that can go into a simple ToolTip.
This is what I ended up doing:
<ToolTipService.ToolTip>
<TextBlock >The first line<LineBreak/>The second line</TextBlock>
</ToolTipService.ToolTip>
Thanks,
Will